diff --git a/browser/base/content/browser.xul b/browser/base/content/browser.xul
index 89df90f1eadf..8b2312b2b622 100644
--- a/browser/base/content/browser.xul
+++ b/browser/base/content/browser.xul
@@ -799,7 +799,6 @@
                      autocompletesearchparam="enable-actions"
                      autocompletepopup="PopupAutoCompleteRichResult"
                      completeselectedindex="true"
-                     shrinkdelay="250"
                      tabscrolling="true"
                      newlines="stripsurroundingwhitespace"
                      ontextentered="this.handleCommand(param);"
diff --git a/browser/base/content/test/performance/browser_urlbar_keyed_search.js b/browser/base/content/test/performance/browser_urlbar_keyed_search.js
index 6c9c91d5e3e8..48ef5afa0ccf 100644
--- a/browser/base/content/test/performance/browser_urlbar_keyed_search.js
+++ b/browser/base/content/test/performance/browser_urlbar_keyed_search.js
@@ -30,22 +30,6 @@ const EXPECTED_REFLOWS_FIRST_OPEN = [
     ],
   },
 
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "onxblpopupshown@chrome://global/content/bindings/autocomplete.xml"
-    ],
-    maxCount: 5, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "_invalidate/this._adjustHeightTimeout<@chrome://global/content/bindings/autocomplete.xml",
-    ],
-    maxCount: 51, // This number should only ever go down - never up.
-  },
-
   {
     stack: [
       "_handleOverflow@chrome://global/content/bindings/autocomplete.xml",
diff --git a/browser/base/content/test/performance/browser_urlbar_search.js b/browser/base/content/test/performance/browser_urlbar_search.js
index bb38bcf93d79..9285fd6c3e01 100644
--- a/browser/base/content/test/performance/browser_urlbar_search.js
+++ b/browser/base/content/test/performance/browser_urlbar_search.js
@@ -30,22 +30,6 @@ const EXPECTED_REFLOWS_FIRST_OPEN = [
     ],
   },
 
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "onxblpopupshown@chrome://global/content/bindings/autocomplete.xml"
-    ],
-    maxCount: 5, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "_invalidate/this._adjustHeightTimeout<@chrome://global/content/bindings/autocomplete.xml",
-    ],
-    maxCount: 6, // This number should only ever go down - never up.
-  },
-
   {
     stack: [
       "_handleOverflow@chrome://global/content/bindings/autocomplete.xml",
@@ -83,22 +67,6 @@ const EXPECTED_REFLOWS_FIRST_OPEN = [
 
 /* These reflows happen everytime the awesomebar panel opens. */
 const EXPECTED_REFLOWS_SECOND_OPEN = [
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "onxblpopupshown@chrome://global/content/bindings/autocomplete.xml"
-    ],
-    maxCount: 3, // This number should only ever go down - never up.
-  },
-
-  {
-    stack: [
-      "adjustHeight@chrome://global/content/bindings/autocomplete.xml",
-      "_invalidate/this._adjustHeightTimeout<@chrome://global/content/bindings/autocomplete.xml",
-    ],
-    maxCount: 6, // This number should only ever go down - never up.
-  },
-
   {
     stack: [
       "_handleOverflow@chrome://global/content/bindings/autocomplete.xml",
diff --git a/browser/base/content/urlbarBindings.xml b/browser/base/content/urlbarBindings.xml
index 1d204a7400c4..76e6169d692f 100644
--- a/browser/base/content/urlbarBindings.xml
+++ b/browser/base/content/urlbarBindings.xml
@@ -1911,6 +1911,10 @@ file, You can obtain one at http://mozilla.org/MPL/2.0/.
         document.getAnonymousElementByAttribute(this, "anonid", "footer");
       </field>
 
+      <field name="shrinkDelay" readonly="true">
+        250
+      </field>
+
       <field name="oneOffSearchButtons" readonly="true">
         document.getAnonymousElementByAttribute(this, "anonid",
                                                 "one-off-search-buttons");
@@ -2195,6 +2199,83 @@ file, You can obtain one at http://mozilla.org/MPL/2.0/.
         ]]></body>
       </method>
 
+      <method name="adjustHeight">
+        <body>
+          <![CDATA[
+          // If we were going to shrink later, cancel that for now:
+          if (this._shrinkTimeout) {
+            clearTimeout(this._shrinkTimeout);
+            this._shrinkTimeout = null;
+          }
+          let lastRowCount = this._lastRowCount;
+          // Figure out how many rows to show
+          let rows = this.richlistbox.childNodes;
+          this._lastRowCount = rows.length;
+          let numRows = Math.min(this.matchCount, this.maxRows, rows.length);
+
+          // If we're going from 0 to non-0 rows, we might need to remove
+          // the height attribute to allow the popup to size. The attribute
+          // is set from XUL popup management code.
+          if (!lastRowCount && rows.length) {
+            this.removeAttribute("height");
+          }
+
+          // Default the height to 0 if we have no rows to show
+          let height = 0;
+          if (numRows) {
+            if (!this._rowHeight) {
+              window.promiseDocumentFlushed(() => {
+                if (window.closed) {
+                  return;
+                }
+                this._rowHeight = rows[0].getBoundingClientRect().height;
+                let style = window.getComputedStyle(this.richlistbox);
+
+                let paddingTop = parseInt(style.paddingTop) || 0;
+                let paddingBottom = parseInt(style.paddingBottom) || 0;
+                this._rlbPadding = paddingTop + paddingBottom;
+                // Then re-run - but don't dirty layout from inside this callback.
+                window.requestAnimationFrame(() => this.adjustHeight());
+              });
+              return;
+            }
+
+            // Calculate the height to have the first row to last row shown
+            height = (this._rowHeight * numRows) + this._rlbPadding;
+          }
+
+          let animate = this.getAttribute("dontanimate") != "true";
+          let currentHeight =
+            parseFloat(this.richlistbox.getAttribute("height"), 10) ||
+            parseFloat(this.richlistbox.style.height, 10) ||
+            0; // It's possible we get here when we haven't set height on the richlistbox
+               // yet, which means parseFloat will return NaN. It should return 0 instead.
+          if (height > currentHeight) {
+            // Grow immediately.
+            if (animate) {
+              this.richlistbox.removeAttribute("height");
+              this.richlistbox.style.height = height + "px";
+            } else {
+              this.richlistbox.style.removeProperty("height");
+              this.richlistbox.height = height;
+            }
+          } else if (height < currentHeight) { // Don't shrink if height matches exactly
+            // Delay shrinking to avoid flicker.
+            this._shrinkTimeout = setTimeout(() => {
+              this._collapseUnusedItems();
+              if (animate) {
+                this.richlistbox.removeAttribute("height");
+                this.richlistbox.style.height = height + "px";
+              } else {
+                this.richlistbox.style.removeProperty("height");
+                this.richlistbox.height = height;
+              }
+            }, this.shrinkDelay);
+          }
+          ]]>
+        </body>
+      </method>
+
       <method name="_showSearchSuggestionsNotification">
         <parameter name="whichNotification"/>
         <parameter name="popupDirection"/>
diff --git a/toolkit/content/widgets/autocomplete.xml b/toolkit/content/widgets/autocomplete.xml
index 514f7595266e..5743ff03e28d 100644
--- a/toolkit/content/widgets/autocomplete.xml
+++ b/toolkit/content/widgets/autocomplete.xml
@@ -131,10 +131,6 @@
       <property name="searchCount" readonly="true"
                 onget="this.initSearchNames(); return this.mSearchNames.length;"/>
 
-      <field name="shrinkDelay" readonly="true">
-        parseInt(this.getAttribute("shrinkdelay")) || 0
-      </field>
-
       <property name="PrivateBrowsingUtils" readonly="true">
         <getter><![CDATA[
           let module = {};
@@ -657,7 +653,6 @@
       <field name="mInput">null</field>
       <field name="mPopupOpen">false</field>
       <field name="_currentIndex">0</field>
-      <field name="_rlbAnimated">false</field>
 
       <!-- =================== nsIAutoCompletePopup =================== -->
 
@@ -826,16 +821,14 @@
           this.richlistbox.collapsed = (this.matchCount == 0);
 
           // Update the richlistbox height.
-          if (this._adjustHeightTimeout) {
-            clearTimeout(this._adjustHeightTimeout);
-          }
-          if (this._shrinkTimeout) {
-            clearTimeout(this._shrinkTimeout);
+          if (this._adjustHeightRAFToken) {
+            cancelAnimationFrame(this._adjustHeightRAFToken);
+            this._adjustHeightRAFToken = null;
           }
 
           if (this.mPopupOpen) {
             delete this._adjustHeightOnPopupShown;
-            this._adjustHeightTimeout = setTimeout(() => this.adjustHeight(), 0);
+            this._adjustHeightRAFToken = requestAnimationFrame(() => this.adjustHeight());
           } else {
             this._adjustHeightOnPopupShown = true;
           }
@@ -896,31 +889,17 @@
           let rows = this.richlistbox.childNodes;
           let numRows = Math.min(this.matchCount, this.maxRows, rows.length);
 
-          this.removeAttribute("height");
-
           // Default the height to 0 if we have no rows to show
           let height = 0;
           if (numRows) {
             let firstRowRect = rows[0].getBoundingClientRect();
             if (this._rlbPadding == undefined) {
               let style = window.getComputedStyle(this.richlistbox);
-
-              let transition = style.transitionProperty;
-              this._rlbAnimated = transition && transition != "none";
-
               let paddingTop = parseInt(style.paddingTop) || 0;
               let paddingBottom = parseInt(style.paddingBottom) || 0;
               this._rlbPadding = paddingTop + paddingBottom;
             }
 
-            if (numRows > this.maxRows) {
-              // Set a fixed max-height to avoid flicker when growing the panel.
-              let lastVisibleRowRect = rows[this.maxRows - 1].getBoundingClientRect();
-              let visibleHeight = lastVisibleRowRect.bottom - firstRowRect.top;
-              this.richlistbox.style.maxHeight =
-                visibleHeight + this._rlbPadding + "px";
-            }
-
             // The class `forceHandleUnderflow` is for the item might need to
             // handle OverUnderflow or Overflow when the height of an item will
             // be changed dynamically.
@@ -936,31 +915,12 @@
                      this._rlbPadding;
           }
 
-          let animate = this._rlbAnimated &&
-                        this.getAttribute("dontanimate") != "true";
           let currentHeight = this.richlistbox.getBoundingClientRect().height;
-          if (height > currentHeight) {
-            // Grow immediately.
-            if (animate) {
-              this.richlistbox.removeAttribute("height");
-              this.richlistbox.style.height = height + "px";
-            } else {
-              this.richlistbox.style.removeProperty("height");
-              this.richlistbox.height = height;
-            }
-          } else {
-            // Delay shrinking to avoid flicker.
-            this._shrinkTimeout = setTimeout(() => {
-              this._collapseUnusedItems();
-              if (animate) {
-                this.richlistbox.removeAttribute("height");
-                this.richlistbox.style.height = height + "px";
-              } else {
-                this.richlistbox.style.removeProperty("height");
-                this.richlistbox.height = height;
-              }
-            }, this.mInput.shrinkDelay);
+          if (height <= currentHeight) {
+            this._collapseUnusedItems();
           }
+          this.richlistbox.style.removeProperty("height");
+          this.richlistbox.height = height;
           ]]>
         </body>
       </method>