Bug 1054901 - Add AsyncPanZoomStarted/Stopped notifications to scroll observers. r=roc

docshell/base/nsDocShell.cpp

@@ -2896,6 +2896,36 @@ nsDocShell::RemoveWeakScrollObserver(nsIScrollObserver* aObserver)
     return mScrollObservers.RemoveElement(obs) ? NS_OK : NS_ERROR_FAILURE;
 }
 
+void
+nsDocShell::NotifyAsyncPanZoomStarted()
+{
+    nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mScrollObservers);
+    while (iter.HasMore()) {
+        nsWeakPtr ref = iter.GetNext();
+        nsCOMPtr<nsIScrollObserver> obs = do_QueryReferent(ref);
+        if (obs) {
+            obs->AsyncPanZoomStarted();
+        } else {
+            mScrollObservers.RemoveElement(ref);
+        }
+    }
+}
+
+void
+nsDocShell::NotifyAsyncPanZoomStopped()
+{
+    nsTObserverArray<nsWeakPtr>::ForwardIterator iter(mScrollObservers);
+    while (iter.HasMore()) {
+        nsWeakPtr ref = iter.GetNext();
+        nsCOMPtr<nsIScrollObserver> obs = do_QueryReferent(ref);
+        if (obs) {
+            obs->AsyncPanZoomStopped();
+        } else {
+            mScrollObservers.RemoveElement(ref);
+        }
+    }
+}
+
 NS_IMETHODIMP
 nsDocShell::NotifyScrollObservers()
 {

docshell/base/nsDocShell.h

@@ -243,6 +243,13 @@ public:
     }
 
     nsresult HistoryTransactionRemoved(int32_t aIndex);
+
+    // Notify Scroll observers when an async panning/zooming transform
+    // has started being applied
+    void NotifyAsyncPanZoomStarted();
+    // Notify Scroll observers when an async panning/zooming transform
+    // is no longer applied
+    void NotifyAsyncPanZoomStopped();
 protected:
     // Object Management
     virtual ~nsDocShell();

docshell/base/nsIScrollObserver.h

@@ -9,8 +9,8 @@
 #include "nsISupports.h"
 
 #define NS_ISCROLLOBSERVER_IID \
-  { 0x7c1a8b63, 0xe322, 0x4827, \
-    { 0xa4, 0xb1, 0x3b, 0x6e, 0x59, 0x03, 0x47, 0x7e } }
+  { 0x03465b77, 0x9ce2, 0x4d19, \
+    { 0xb2, 0xf6, 0x82, 0xae, 0xee, 0x85, 0xc3, 0xbf } }
 
 class nsIScrollObserver : public nsISupports
 {
@@ -21,6 +21,16 @@ public:
    * Called when the scroll position of some element has changed.
    */
   virtual void ScrollPositionChanged() = 0;
+
+  /**
+   * Called when an async panning/zooming transform has started being applied.
+   */
+  virtual void AsyncPanZoomStarted(){};
+
+  /**
+   * Called when an async panning/zooming transform is no longer applied.
+   */
+  virtual void AsyncPanZoomStopped(){};
 };
 
 NS_DEFINE_STATIC_IID_ACCESSOR(nsIScrollObserver, NS_ISCROLLOBSERVER_IID)

dom/ipc/TabChild.cpp

@@ -34,6 +34,7 @@
 #include "mozilla/unused.h"
 #include "mozIApplication.h"
 #include "nsContentUtils.h"
+#include "nsDocShell.h"
 #include "nsEmbedCID.h"
 #include <algorithm>
 #ifdef MOZ_CRASHREPORTER
@@ -1873,6 +1874,15 @@ TabChild::RecvNotifyAPZStateChange(const ViewID& aViewId,
     if (scrollbarOwner) {
       scrollbarOwner->ScrollbarActivityStarted();
     }
+
+    nsCOMPtr<nsIDocument> doc = GetDocument();
+    if (doc) {
+      nsCOMPtr<nsIDocShell> docshell(doc->GetDocShell());
+      if (docshell) {
+        nsDocShell* nsdocshell = static_cast<nsDocShell*>(docshell.get());
+        nsdocshell->NotifyAsyncPanZoomStarted();
+      }
+    }
     break;
   }
   case APZStateChange::TransformEnd:
@@ -1882,6 +1892,15 @@ TabChild::RecvNotifyAPZStateChange(const ViewID& aViewId,
     if (scrollbarOwner) {
       scrollbarOwner->ScrollbarActivityStopped();
     }
+
+    nsCOMPtr<nsIDocument> doc = GetDocument();
+    if (doc) {
+      nsCOMPtr<nsIDocShell> docshell(doc->GetDocShell());
+      if (docshell) {
+        nsDocShell* nsdocshell = static_cast<nsDocShell*>(docshell.get());
+        nsdocshell->NotifyAsyncPanZoomStopped();
+      }
+    }
     break;
   }
   case APZStateChange::StartTouch: