Add support to delay sending SwapbufferAck as needed.

content/common/gpu/image_transport_surface.cc

Index: content/common/gpu/image_transport_surface.cc
diff --git a/content/common/gpu/image_transport_surface.cc b/content/common/gpu/image_transport_surface.cc
index f4c5a68cb218b02b354c2612ec7f3b18b4e89b63..6d7f4a420928169eba9cd1770dadd4d74df706ce 100644
--- a/content/common/gpu/image_transport_surface.cc
+++ b/content/common/gpu/image_transport_surface.cc
@@ -119,9 +119,14 @@ void ImageTransportHelper::SendUpdateVSyncParameters(
                                                       interval));
 }
 
-void ImageTransportHelper::SwapBuffersCompleted(
-    const std::vector<ui::LatencyInfo>& latency_info) {
-  stub_->SwapBuffersCompleted(latency_info);
+void ImageTransportHelper::SwapBuffersCallBack() {
+  for (size_t i = 0; i < latency_info_.size(); i++) {
+    latency_info_[i].AddLatencyNumber(
+        ui::INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT, 0, 0);
+  }
+
+  stub_->SwapBuffersCompleted(latency_info_);
+  latency_info_.clear();
 }
 
 void ImageTransportHelper::SetPreemptByFlag(
@@ -179,7 +184,8 @@ void ImageTransportHelper::Resize(gfx::Size size, float scale_factor) {
 
 void ImageTransportHelper::SetLatencyInfo(
     const std::vector<ui::LatencyInfo>& latency_info) {
-  surface_->SetLatencyInfo(latency_info);

[piman, 2014/12/22 20:53:15]

Why this change? I don't understand...
It will break cases where |surface_| is not a PassThroughImageTransportSurface
(e.g. mac's ImageTransportSurfaceFBO).

Why not keeping the code where it is, but taking a WeakPtr on the
PassThroughImageTransportSurface?

[kalyank, 2014/12/23 09:12:32]

ImageTransportSurfaceAndroid inherits base::SupportsWeakPtr and
NullTransportSurface (NullTransportSurface inherits
PassThroughImageTransportSurface) . This was causing an issue, I tried changing
so that ImageTransportSurfaceAndroid doesn't inherit base::SupportsWeakPtr, but
it obviously complains in line 107 image_transport_surface_android.cc "
../../base/bind_internal.h:882:18: error: cannot initialize a parameter of type
'content::ImageTransportSurfaceAndroid *' with an rvalue of type
'content::PassThroughImageTransportSurface *'
    runnable.Run(weak_ptr.get());
"

Any suggestions ?

[kalyank, 2014/12/23 11:22:42]

Added ImageTransportHelperAndroid, which will be used by
ImageTransportSurfaceAndroid to handle callbacks.

+  for (size_t i = 0; i < latency_info.size(); i++)
+    latency_info_.push_back(latency_info[i]);
 }
 
 PassThroughImageTransportSurface::PassThroughImageTransportSurface(
@@ -205,37 +211,32 @@ void PassThroughImageTransportSurface::Destroy() {
 
 void PassThroughImageTransportSurface::SetLatencyInfo(
     const std::vector<ui::LatencyInfo>& latency_info) {
-  for (size_t i = 0; i < latency_info.size(); i++)
-    latency_info_.push_back(latency_info[i]);
+  helper_->SetLatencyInfo(latency_info);
 }
 
 bool PassThroughImageTransportSurface::SwapBuffers() {
   // GetVsyncValues before SwapBuffers to work around Mali driver bug:
   // crbug.com/223558.
   SendVSyncUpdateIfAvailable();
-  bool result = gfx::GLSurfaceAdapter::SwapBuffers();
-  for (size_t i = 0; i < latency_info_.size(); i++) {
-    latency_info_[i].AddLatencyNumber(
-        ui::INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT, 0, 0);
-  }
-
-  helper_->SwapBuffersCompleted(latency_info_);
-  latency_info_.clear();
-  return result;
+  // We use WeakPtr here to avoid manual management of life time of an instance
+  // of this class. Callback will not be called once the instance of this class
+  // is destroyed. However, this also means that the callback can be run on
+  // GPUMainThread only.
+  return gfx::GLSurfaceAdapter::SwapBuffersAsync(
+      base::Bind(&ImageTransportHelper::SwapBuffersCallBack,
+          helper_->AsWeakPtr()));
 }
 
 bool PassThroughImageTransportSurface::PostSubBuffer(
     int x, int y, int width, int height) {
   SendVSyncUpdateIfAvailable();
-  bool result = gfx::GLSurfaceAdapter::PostSubBuffer(x, y, width, height);
-  for (size_t i = 0; i < latency_info_.size(); i++) {
-    latency_info_[i].AddLatencyNumber(
-        ui::INPUT_EVENT_LATENCY_TERMINATED_FRAME_SWAP_COMPONENT, 0, 0);
-  }
-
-  helper_->SwapBuffersCompleted(latency_info_);
-  latency_info_.clear();
-  return result;
+  // We use WeakPtr here to avoid manual management of life time of an instance
+  // of this class. Callback will not be called once the instance of this class
+  // is destroyed. However, this also means that the callback can be run on
+  // GPUMainThread only.
+  return gfx::GLSurfaceAdapter::PostSubBufferAsync(x, y, width, height,
+      base::Bind(&ImageTransportHelper::SwapBuffersCallBack,
+          helper_->AsWeakPtr()));
 }
 
 bool PassThroughImageTransportSurface::OnMakeCurrent(gfx::GLContext* context) {