diff --git a/layout/mathml/nsMathMLmencloseFrame.cpp b/layout/mathml/nsMathMLmencloseFrame.cpp
index 6385ac9434f9..3ab5a7364f9f 100644
--- a/layout/mathml/nsMathMLmencloseFrame.cpp
+++ b/layout/mathml/nsMathMLmencloseFrame.cpp
@@ -28,6 +28,9 @@ static const char16_t kRadicalChar = 0x221A;
 // updiagonalstrike
 static const uint8_t kArrowHeadSize = 10;
 
+// phasorangle
+static const uint8_t kPhasorangleWidth = 8;
+
 nsIFrame*
 NS_NewMathMLmencloseFrame(nsIPresShell* aPresShell, nsStyleContext* aContext)
 {
@@ -122,6 +125,8 @@ nsresult nsMathMLmencloseFrame::AddNotation(const nsAString& aNotation)
     mNotationsToDraw |= NOTATION_HORIZONTALSTRIKE;
   } else if (aNotation.EqualsLiteral("madruwb")) {
     mNotationsToDraw |= (NOTATION_RIGHT | NOTATION_BOTTOM);
+  } else if (aNotation.EqualsLiteral("phasorangle")) {
+    mNotationsToDraw |= (NOTATION_BOTTOM | NOTATION_PHASORANGLE);
   }
 
   return NS_OK;
@@ -211,6 +216,11 @@ nsMathMLmencloseFrame::BuildDisplayList(nsDisplayListBuilder*   aBuilder,
     DisplayBar(aBuilder, this, rect, aLists);
   }
 
+  if (IsToDraw(NOTATION_PHASORANGLE)) {
+    DisplayNotation(aBuilder, this, mencloseRect, aLists,
+                mRuleThickness, NOTATION_PHASORANGLE);
+  }
+
   if (IsToDraw(NOTATION_LONGDIV)) {
     mMathMLChar[mLongDivCharIndex].Display(aBuilder, this, aLists, 1);
 
@@ -387,7 +397,8 @@ nsMathMLmencloseFrame::PlaceInternal(nsRenderingContext& aRenderingContext,
       IsToDraw(NOTATION_CIRCLE) ||
       IsToDraw(NOTATION_ROUNDEDBOX) ||
       IsToDraw(NOTATION_RADICAL) ||
-      IsToDraw(NOTATION_LONGDIV)) {
+      IsToDraw(NOTATION_LONGDIV) ||
+      IsToDraw(NOTATION_PHASORANGLE)) {
       // set a minimal value for the base height
       bmBase.ascent = std::max(bmOne.ascent, bmBase.ascent);
       bmBase.descent = std::max(0, bmBase.descent);
@@ -410,6 +421,14 @@ nsMathMLmencloseFrame::PlaceInternal(nsRenderingContext& aRenderingContext,
       IsToDraw(NOTATION_CIRCLE))
     mBoundingMetrics.descent += padding;
 
+   ///////////////
+   // phasorangle notation
+  if (IsToDraw(NOTATION_PHASORANGLE)) {
+    nscoord phasorangleWidth = kPhasorangleWidth * mRuleThickness;
+    // Update horizontal parameters
+    dx_left = std::max(dx_left, phasorangleWidth);
+  }
+
   ///////////////
   // updiagonal arrow notation. We need enough space at the top right corner to
   // draw the arrow head.
@@ -613,6 +632,11 @@ nsMathMLmencloseFrame::PlaceInternal(nsRenderingContext& aRenderingContext,
       IsToDraw(NOTATION_ROUNDEDBOX))
     mBoundingMetrics.descent = aDesiredSize.Height() - aDesiredSize.TopAscent();
 
+  // phasorangle notation:
+  // move up from the bottom by the angled line height
+  if (IsToDraw(NOTATION_PHASORANGLE))
+    mBoundingMetrics.ascent = std::max(mBoundingMetrics.ascent, 2 * kPhasorangleWidth * mRuleThickness - mBoundingMetrics.descent);
+  
   aDesiredSize.mBoundingMetrics = mBoundingMetrics;
   
   mReference.x = 0;
@@ -802,6 +826,20 @@ void nsDisplayNotation::Paint(nsDisplayListBuilder* aBuilder,
     }
       break;
 
+    case NOTATION_PHASORANGLE: {
+      // Compute some parameters to draw the angled line,
+      // that uses a slope of 2 (angle = tan^-1(2)).
+      // H = w * tan(angle) = w * 2
+      gfxFloat w = gfxFloat(kPhasorangleWidth) * e;
+      gfxFloat H = 2 * w;
+
+      // Draw the angled line
+      gfxCtx->NewPath();
+      gfxCtx->Line(rect.BottomLeft(), rect.BottomLeft() + gfxPoint(w, -H));
+      gfxCtx->Stroke();
+      break;
+    }
+
     default:
       NS_NOTREACHED("This notation can not be drawn using nsDisplayNotation");
       break;
diff --git a/layout/mathml/nsMathMLmencloseFrame.h b/layout/mathml/nsMathMLmencloseFrame.h
index df909d0f471f..2d0554aebd64 100644
--- a/layout/mathml/nsMathMLmencloseFrame.h
+++ b/layout/mathml/nsMathMLmencloseFrame.h
@@ -38,7 +38,8 @@ enum nsMencloseNotation
     NOTATION_DOWNDIAGONALSTRIKE = 0x200,
     NOTATION_VERTICALSTRIKE = 0x400,
     NOTATION_HORIZONTALSTRIKE = 0x800,
-    NOTATION_UPDIAGONALARROW = 0x1000
+    NOTATION_UPDIAGONALARROW = 0x1000,
+    NOTATION_PHASORANGLE = 0x2000
   };
 
 class nsMathMLmencloseFrame : public nsMathMLContainerFrame {
diff --git a/layout/reftests/mathml/menclose-1q.html b/layout/reftests/mathml/menclose-1q.html
new file mode 100644
index 000000000000..0e185e72fc4b
--- /dev/null
+++ b/layout/reftests/mathml/menclose-1q.html
@@ -0,0 +1,13 @@
+<!DOCTYPE html>
+<html>
+  <head>
+    <title>Test menclose</title>
+  </head>
+  <body>   
+    <math>
+      <menclose notation="phasorangle">
+        <mspace width="100px" height="50px"></mspace>
+      </menclose>
+    </math>
+  </body>
+</html>
diff --git a/layout/reftests/mathml/menclose-2-phasorangle-ref.html b/layout/reftests/mathml/menclose-2-phasorangle-ref.html
new file mode 100644
index 000000000000..da18a54b98a1
--- /dev/null
+++ b/layout/reftests/mathml/menclose-2-phasorangle-ref.html
@@ -0,0 +1,41 @@
+<!doctype html>
+<html class="reftest-wait">
+  <head>
+    <title>menclose phasorangle</title>
+    <meta charset="utf-8"/>
+    <script type="text/javascript">
+      function doTest()
+      {
+        var box = document.getElementById("box").getBoundingClientRect();
+        var w = 8 * 2; // kPhasorangleWidth * rulethickness
+        var H = 2 * w; // slope 2
+
+        document.getElementById("path").setAttribute("d",
+          "M" + (box.right + "," + box.bottom) +
+          "L" + (box.left + "," + box.bottom ) +
+          "l" + ((w) + "," + (-H)));
+        document.documentElement.removeAttribute("class");
+      }
+      window.addEventListener("MozReftestInvalidate", doTest, false);
+    </script>
+  </head>
+  <body>
+
+    <div style="position: absolute; left: 20px; top: 20px;">
+      <math>
+        <mphantom>
+          <menclose id="box" notation="phasorangle">
+            <mspace width="200px" height="100px"></mspace>
+          </menclose>
+        </mphantom>
+      </math>
+    </div>
+
+    <div style="position: absolute; left: 0px; top: 0px;">
+      <svg width="500px" height="500px">
+        <path id="path" style="fill: none; stroke-width: 5px; stroke: green; stroke-linecap: round; shape-rendering: crispEdges;"></path>
+      </svg>
+    </div>
+    
+  </body>
+</html>
diff --git a/layout/reftests/mathml/menclose-2-phasorangle.html b/layout/reftests/mathml/menclose-2-phasorangle.html
new file mode 100644
index 000000000000..a8ffbb90b1ad
--- /dev/null
+++ b/layout/reftests/mathml/menclose-2-phasorangle.html
@@ -0,0 +1,39 @@
+<!doctype html>
+<html class="reftest-wait">
+  <head>
+    <title>menclose phasorangle</title>
+    <meta charset="utf-8"/>
+    <script type="text/javascript">
+      function doTest()
+      {
+        var box = document.getElementById("box").getBoundingClientRect();
+        var w = 8 * 2; // kPhasorangleWidth * rulethickness
+        var H = 2 * w; // slope 2
+
+        document.getElementById("path").setAttribute("d",
+          "M" + (box.right + "," + box.bottom) +
+          "L" + (box.left + "," + box.bottom ) +
+          "l" + ((w) + "," + (-H)));
+        document.documentElement.removeAttribute("class");
+      }
+      window.addEventListener("MozReftestInvalidate", doTest, false);
+    </script>
+  </head>
+  <body>
+
+    <div style="position: absolute; left: 20px; top: 20px;">
+      <math>
+        <menclose id="box" notation="phasorangle">
+          <mspace width="200px" height="100px"></mspace>
+        </menclose>
+      </math>
+    </div>
+
+    <div style="position: absolute; left: 0px; top: 0px;">
+      <svg width="500px" height="500px">
+        <path id="path" style="fill: none; stroke-width: 5px; stroke: green; stroke-linecap: round; shape-rendering: crispEdges;"></path>
+      </svg>
+    </div>
+    
+  </body>
+</html>
diff --git a/layout/reftests/mathml/menclose-5-phasorangle-ref.html b/layout/reftests/mathml/menclose-5-phasorangle-ref.html
new file mode 100644
index 000000000000..e8cc53a51096
--- /dev/null
+++ b/layout/reftests/mathml/menclose-5-phasorangle-ref.html
@@ -0,0 +1,11 @@
+<!doctype html>
+<html>
+  <head>
+    <title>menclose actuarial</title>
+	</head>
+  <body>
+    <p>
+      <math><menclose id="testMenclose" notation="phasorangle"><mspace width="100px" height="50px"></menclose></math>
+    </p>
+  </body>
+</html>
diff --git a/layout/reftests/mathml/menclose-5-phasorangle.html b/layout/reftests/mathml/menclose-5-phasorangle.html
new file mode 100644
index 000000000000..a880ab24f09f
--- /dev/null
+++ b/layout/reftests/mathml/menclose-5-phasorangle.html
@@ -0,0 +1,18 @@
+<!doctype html>
+<html class="reftest-wait">
+  <head>
+    <title>menclose phasorangle</title>
+      <script type="text/javascript">
+        function doTest() {
+          document.getElementById('testMenclose').setAttribute("notation","phasorangle");
+          document.documentElement.removeAttribute("class");
+        }
+        window.addEventListener("MozReftestInvalidate", doTest, false);
+      </script>
+  </head>
+  <body>
+    <p>
+      <math><menclose id="testMenclose"><mspace width="100px" height="50px"></menclose></math>
+    </p>
+  </body>
+</html>
diff --git a/layout/reftests/mathml/menclose-6-phasorangle.html b/layout/reftests/mathml/menclose-6-phasorangle.html
new file mode 100644
index 000000000000..5cb5e6ace17e
--- /dev/null
+++ b/layout/reftests/mathml/menclose-6-phasorangle.html
@@ -0,0 +1,22 @@
+<!doctype html>
+<html class="reftest-wait">
+  <head>
+    <title>menclose phasorangle</title>
+    <script type="text/javascript">
+      function doTest() {
+        document.getElementById('testMenclose').removeAttribute("notation");
+        document.documentElement.removeAttribute("class");
+      }
+      window.addEventListener("MozReftestInvalidate", doTest, false);
+    </script>
+  </head>
+  <body>
+    <p>
+      <math>
+        <menclose id="testMenclose" notation="phasorangle">
+          <mspace width="100px" height="50px" mathbackground="blue"></mspace>
+        </menclose>
+      </math>
+    </p>
+	</body>
+</html>
diff --git a/layout/reftests/mathml/reftest.list b/layout/reftests/mathml/reftest.list
index a7e5b55521a5..aa9cf0bc59d1 100644
--- a/layout/reftests/mathml/reftest.list
+++ b/layout/reftests/mathml/reftest.list
@@ -175,6 +175,7 @@ fails-if(B2G) == multiscripts-1.html multiscripts-1-ref.html # B2G - slight heig
 != menclose-1n.html menclose-1-ref.html
 != menclose-1o.html menclose-1-ref.html
 != menclose-1p.html menclose-1-ref.html
+!= menclose-1q.html menclose-1-ref.html
 fails-if(B2G) == menclose-2-actuarial.html menclose-2-actuarial-ref.html # B2G slight thickness variation
 == menclose-2-bottom.html menclose-2-bottom-ref.html
 fails-if(B2G) == menclose-2-box.html menclose-2-box-ref.html # B2G slight thickness variation
@@ -190,6 +191,7 @@ fails-if(B2G) == menclose-2-updiagonalarrow.html menclose-2-updiagonalarrow-ref.
 == menclose-2-updiagonalstrike.html menclose-2-updiagonalstrike-ref.html
 == menclose-2-verticalstrike.html menclose-2-verticalstrike-ref.html
 fails-if(B2G) == menclose-2-roundedbox.html menclose-2-roundedbox-ref.html # B2G slight thickness variation
+== menclose-2-phasorangle.html menclose-2-phasorangle-ref.html
 == menclose-3-box.html menclose-3-box-ref.html
 == menclose-3-madruwb.html menclose-3-madruwb-ref.html
 fails random-if(winWidget) == menclose-3-radical.html menclose-3-radical-ref.html # Bug 973917
@@ -214,6 +216,7 @@ fuzzy-if(OSX,1,100) == menclose-5-circle.html menclose-5-circle-ref.html
 == menclose-5-updiagonalarrow.html menclose-5-updiagonalarrow-ref.html
 == menclose-5-updiagonalstrike.html menclose-5-updiagonalstrike-ref.html
 == menclose-5-verticalstrike.html menclose-5-verticalstrike-ref.html
+== menclose-5-phasorangle.html menclose-5-phasorangle-ref.html
 == menclose-6-actuarial.html menclose-6-ref.html
 == menclose-6-bottom.html menclose-6-ref.html
 == menclose-6-box.html menclose-6-ref.html
@@ -230,6 +233,7 @@ fuzzy-if(OSX,1,100) == menclose-5-circle.html menclose-5-circle-ref.html
 == menclose-6-updiagonalarrow.html menclose-6-ref.html
 == menclose-6-updiagonalstrike.html menclose-6-ref.html
 == menclose-6-verticalstrike.html menclose-6-ref.html
+== menclose-6-phasorangle.html menclose-6-ref.html
 == mmultiscript-align.html mmultiscript-align-ref.html
 == subscript-italic-correction.html subscript-italic-correction-ref.html
 == mathvariant-1a.html mathvariant-1a-ref.html