Revamp OffscreenCanvas commit flow

third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp

Index: third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
diff --git a/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp b/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
index 4355caed2a27dd712a886705e5bd9e97539d3cf5..0b93b88a7dd728a992615038f64c80274b25fc03 100644
--- a/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
+++ b/third_party/WebKit/Source/platform/graphics/CanvasSurfaceLayerBridge.cpp
@@ -4,6 +4,7 @@
 
 #include "platform/graphics/CanvasSurfaceLayerBridge.h"
 
+#include "cc/layers/solid_color_layer.h"
 #include "cc/layers/surface_layer.h"
 #include "cc/surfaces/surface_id.h"
 #include "cc/surfaces/surface_sequence.h"
@@ -18,31 +19,56 @@
 namespace blink {
 
 CanvasSurfaceLayerBridge::CanvasSurfaceLayerBridge(
-    mojom::blink::OffscreenCanvasSurfacePtr service)
-    : m_service(std::move(service)) {}
-
-CanvasSurfaceLayerBridge::~CanvasSurfaceLayerBridge() {}
-
-bool CanvasSurfaceLayerBridge::createSurfaceLayer(int canvasWidth,
-                                                  int canvasHeight) {
-  if (!m_service->GetSurfaceId(&m_surfaceId))
-    return false;
-
-  cc::SurfaceLayer::SatisfyCallback satisfyCallback =
-      convertToBaseCallback(WTF::bind(
-          &CanvasSurfaceLayerBridge::satisfyCallback, WTF::unretained(this)));
-  cc::SurfaceLayer::RequireCallback requireCallback =
-      convertToBaseCallback(WTF::bind(
-          &CanvasSurfaceLayerBridge::requireCallback, WTF::unretained(this)));
-  m_surfaceLayer = cc::SurfaceLayer::Create(std::move(satisfyCallback),
-                                            std::move(requireCallback));
-  m_surfaceLayer->SetSurfaceId(m_surfaceId, 1.f,
-                               gfx::Size(canvasWidth, canvasHeight));
+    mojom::blink::OffscreenCanvasSurfacePtr service,
+    CanvasSurfaceLayerBridgeObserver* observer)
+    : m_observer(observer),
+      m_service(std::move(service)),
+      m_binding(this),
+      m_frameSinkId(Platform::current()->generateFrameSinkId()) {
+  // This FrameSinkId will be used throughout the lifecycle of this canvas.
+  m_service->SetClient(m_binding.CreateInterfacePtrAndBind(), m_frameSinkId);
+}
+
+CanvasSurfaceLayerBridge::~CanvasSurfaceLayerBridge() {
+  m_observer = nullptr;
+}
 
+void CanvasSurfaceLayerBridge::createSolidColorLayer() {
+  m_solidColorLayer = cc::SolidColorLayer::Create();
+  m_solidColorLayer->SetBackgroundColor(SK_ColorTRANSPARENT);
   m_webLayer = Platform::current()->compositorSupport()->createLayerFromCCLayer(
-      m_surfaceLayer.get());
+      m_solidColorLayer.get());
   GraphicsLayer::registerContentsLayer(m_webLayer.get());
-  return true;
+}
+
+void CanvasSurfaceLayerBridge::OnSurfaceCreated(const cc::SurfaceId& surfaceId,
+                                                int32_t width,
+                                                int32_t height,
+                                                float deviceScaleFactor) {
+  if (!m_currentSurfaceId.is_valid() || surfaceId != m_currentSurfaceId) {
+    m_currentSurfaceId = surfaceId;
+
+    cc::SurfaceLayer::SatisfyCallback satisfyCallback =
+        convertToBaseCallback(WTF::bind(
+            &CanvasSurfaceLayerBridge::satisfyCallback, WTF::unretained(this)));
+    cc::SurfaceLayer::RequireCallback requireCallback =
+        convertToBaseCallback(WTF::bind(
+            &CanvasSurfaceLayerBridge::requireCallback, WTF::unretained(this)));
+    m_surfaceLayer = cc::SurfaceLayer::Create(std::move(satisfyCallback),
+                                              std::move(requireCallback));
+    m_surfaceLayer->SetSurfaceId(m_currentSurfaceId, deviceScaleFactor,
+                                 gfx::Size(width, height));
+
+    GraphicsLayer::unregisterContentsLayer(m_webLayer.get());
+    m_webLayer->removeFromParent();
+
+    m_webLayer =

[Fady Samuel, 2016/12/15 19:54:52]

You don't need to create a new layer every time the surfaceId changes. Only when
it was invalid and now is valid.

[xlai (Olivia), 2016/12/15 22:20:12]

Done. But I'm wondering, when SurfaceId, and possibly dsf, size is changed, do I
just need to call SetSurfaceId function to replace the attribute values on the
existing SurfaceLayer? <== this is a question about resizing functionality not
in this patch.

[Fady Samuel, 2016/12/15 22:26:01]

Yes, you just call SetSurfaceId

+        Platform::current()->compositorSupport()->createLayerFromCCLayer(
+            m_surfaceLayer.get());
+    GraphicsLayer::registerContentsLayer(m_webLayer.get());
+
+    m_observer->OnWebLayerReplaced();
+  }
 }
 
 void CanvasSurfaceLayerBridge::satisfyCallback(