2D canvas: fix shadow rendering with compositing modes that require temp layers

Source/core/html/canvas/CanvasRenderingContext2D.cpp

Index: Source/core/html/canvas/CanvasRenderingContext2D.cpp
diff --git a/Source/core/html/canvas/CanvasRenderingContext2D.cpp b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
index a1911e5990147f992e81a3511e0192d35fa2bb4a..c61ac1a91e845b4828b335ec2cbf4e04e62bfa90 100644
--- a/Source/core/html/canvas/CanvasRenderingContext2D.cpp
+++ b/Source/core/html/canvas/CanvasRenderingContext2D.cpp
@@ -1411,7 +1411,7 @@ void CanvasRenderingContext2D::setShadow(const FloatSize& offset, float blur, RG
     applyShadow();
 }
 
-void CanvasRenderingContext2D::applyShadow()
+void CanvasRenderingContext2D::applyShadow(ShadowMode shadowMode)
 {
     GraphicsContext* c = drawingContext();
     if (!c)
@@ -1419,7 +1419,7 @@ void CanvasRenderingContext2D::applyShadow()
 
     if (shouldDrawShadows()) {
         c->setShadow(state().m_shadowOffset, state().m_shadowBlur, state().m_shadowColor,
-            DrawLooperBuilder::ShadowIgnoresTransforms);
+            DrawLooperBuilder::ShadowIgnoresTransforms, DrawLooperBuilder::ShadowRespectsAlpha, shadowMode);
     } else {
         c->clearShadow();
     }
@@ -1646,12 +1646,25 @@ template<class T> void CanvasRenderingContext2D::fullCanvasCompositedFill(const
 
     GraphicsContext* c = drawingContext();
     ASSERT(c);
-    c->beginLayer(1, state().m_globalComposite);
+
     CompositeOperator previousOperator = c->compositeOperation();
+    if (shouldDrawShadows()) {
+        // unroll into two independently composited passes if drawing shadows
+        c->beginLayer(1, state().m_globalComposite);
+        c->setCompositeOperation(CompositeSourceOver);
+        applyShadow(DrawShadowOnly);
+        fillPrimitive(area, c);
+        c->setCompositeOperation(previousOperator);
+        c->endLayer();
+    }
+
+    c->beginLayer(1, state().m_globalComposite);
+    applyShadow(DrawForegroundOnly);
     c->setCompositeOperation(CompositeSourceOver);
     fillPrimitive(area, c);
     c->setCompositeOperation(previousOperator);
     c->endLayer();
+    applyShadow(DrawShadowAndForeground); // go back to normal shadows
 }
 
 static void strokePrimitive(const FloatRect& rect, GraphicsContext* context)
@@ -1670,12 +1683,25 @@ template<class T> void CanvasRenderingContext2D::fullCanvasCompositedStroke(cons
 
     GraphicsContext* c = drawingContext();
     ASSERT(c);
-    c->beginLayer(1, state().m_globalComposite);
+
     CompositeOperator previousOperator = c->compositeOperation();
+    if (shouldDrawShadows()) {
+        // unroll into two independently composited passes if drawing shadows
+        c->beginLayer(1, state().m_globalComposite);
+        c->setCompositeOperation(CompositeSourceOver);
+        applyShadow(DrawShadowOnly);
+        strokePrimitive(area, c);
+        c->setCompositeOperation(previousOperator);
+        c->endLayer();
+    }
+
+    c->beginLayer(1, state().m_globalComposite);
+    applyShadow(DrawForegroundOnly);
     c->setCompositeOperation(CompositeSourceOver);
     strokePrimitive(area, c);
     c->setCompositeOperation(previousOperator);
     c->endLayer();
+    applyShadow(DrawShadowAndForeground); // go back to normal shadows
 }
 
 PassRefPtrWillBeRawPtr<CanvasGradient> CanvasRenderingContext2D::createLinearGradient(float x0, float y0, float x1, float y1)