Move Canvas elements to their own composited layer

This drastically improves performances, as invalidating a canvas
will only touch that one layer instead of (possibly) invalidating the
entire PictureSet.

bug:5247823
Change-Id: Iec4de74d25e58e63f0198bbd7558c461d9a11cfd

2 files changed, 11 insertions, 0 deletions

diff --git a/Source/WebCore/rendering/RenderHTMLCanvas.cpp b/Source/WebCore/rendering/RenderHTMLCanvas.cpp
index de2a2c1..03b406b 100644
--- a/Source/WebCore/rendering/RenderHTMLCanvas.cpp
+++ b/Source/WebCore/rendering/RenderHTMLCanvas.cpp
@@ -47,6 +47,13 @@ RenderHTMLCanvas::RenderHTMLCanvas(HTMLCanvasElement* element)
 
 bool RenderHTMLCanvas::requiresLayer() const
 {
+#if PLATFORM(ANDROID)
+    // All Canvas are drawn on their own composited layer
+    // This improves performances a lot (as this simplify
+    // the repaint/inval chain dealing with the PictureSet)
+    return true;
+#endif
+
     if (RenderReplaced::requiresLayer())
         return true;
     
diff --git a/Source/WebCore/rendering/RenderLayerCompositor.cpp b/Source/WebCore/rendering/RenderLayerCompositor.cpp
index 03f1e41..25a08e7 100644
--- a/Source/WebCore/rendering/RenderLayerCompositor.cpp
+++ b/Source/WebCore/rendering/RenderLayerCompositor.cpp
@@ -1410,6 +1410,10 @@ bool RenderLayerCompositor::requiresCompositingForAndroidLayers(const RenderLaye
     if (layer->isFixed())
         return true;
 #endif
+
+    if (layer->renderer()->isCanvas())
+        return true;
+
     return false;
 }
 #endif