Web setting for canvas2d msaa

Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp

Index: Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
diff --git a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
index 1532d4f9b687e8b48257598849037d27c829ba74..4b6b34ea3e4b9c64aa2b97bd1a36d150c1ba8682 100644
--- a/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
+++ b/Source/core/platform/graphics/chromium/Canvas2DLayerBridge.cpp
@@ -59,7 +59,7 @@ Canvas2DLayerBridgePtr& Canvas2DLayerBridgePtr::operator=(const PassRefPtr<Canva
     return *this;
 }
 
-static SkSurface* createSurface(GraphicsContext3D* context3D, const IntSize& size)
+static SkSurface* createSurface(GraphicsContext3D* context3D, const IntSize& size, int msaaSampleCount)
 {
     ASSERT(!context3D->webContext()->isContextLost());
     GrContext* gr = context3D->grContext();
@@ -71,13 +71,13 @@ static SkSurface* createSurface(GraphicsContext3D* context3D, const IntSize& siz
     info.fHeight = size.height();
     info.fColorType = SkImage::kPMColor_ColorType;
     info.fAlphaType = kPremul_SkAlphaType;
-    return SkSurface::NewRenderTarget(gr, info);
+    return SkSurface::NewRenderTarget(gr, info,  msaaSampleCount);
 }
 
-PassRefPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(PassRefPtr<GraphicsContext3D> context, const IntSize& size, OpacityMode opacityMode)
+PassRefPtr<Canvas2DLayerBridge> Canvas2DLayerBridge::create(PassRefPtr<GraphicsContext3D> context, const IntSize& size, OpacityMode opacityMode, int msaaSampleCount)
 {
     TRACE_EVENT_INSTANT0("test_gpu", "Canvas2DLayerBridgeCreation");
-    SkAutoTUnref<SkSurface> surface(createSurface(context.get(), size));
+    SkAutoTUnref<SkSurface> surface(createSurface(context.get(), size, msaaSampleCount));
     if (!surface.get()) {
         return PassRefPtr<Canvas2DLayerBridge>();
     }
@@ -257,7 +257,8 @@ bool Canvas2DLayerBridge::isValid()
         } else {
             m_context = sharedContext;
             IntSize size(m_canvas->getTopDevice()->width(), m_canvas->getTopDevice()->height());
-            SkAutoTUnref<SkSurface> surface(createSurface(m_context.get(), size));
+            int msaaSampleCount = m_canvas->getTopDevice()->accessRenderTarget()->desc().fSampleCnt;
+            SkAutoTUnref<SkSurface> surface(createSurface(m_context.get(), size, msaaSampleCount));
             if (surface.get()) {
                 m_canvas->setSurface(surface.get());
                 m_surfaceIsValid = true;