Allow CopyFromBackingStore to fallback to copying from the renderer side if the accelerated surface…

content/renderer/render_widget.cc

Index: content/renderer/render_widget.cc
diff --git a/content/renderer/render_widget.cc b/content/renderer/render_widget.cc
index fc69a27aad3ad10442336cb06a2c2102a2948208..05c5f325b0ede927ae8b80c1649a0e789ed4e053 100644
--- a/content/renderer/render_widget.cc
+++ b/content/renderer/render_widget.cc
@@ -5,6 +5,7 @@
 #include "content/renderer/render_widget.h"
 
 #include "base/bind.h"
+#include "base/bind_helpers.h"
 #include "base/command_line.h"
 #include "base/debug/trace_event.h"
 #include "base/logging.h"
@@ -321,6 +322,7 @@ bool RenderWidget::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER(ViewMsg_ImeBatchStateChanged, OnImeBatchStateChanged)
     IPC_MESSAGE_HANDLER(ViewMsg_ShowImeIfNeeded, OnShowImeIfNeeded)
 #endif
+    IPC_MESSAGE_HANDLER(ViewMsg_Snapshot, OnSnapshot)
     IPC_MESSAGE_UNHANDLED(handled = false)
   IPC_END_MESSAGE_MAP()
   return handled;
@@ -1821,6 +1823,53 @@ void RenderWidget::OnPaintAtSize(const TransportDIB::Handle& dib_handle,
   Send(new ViewHostMsg_PaintAtSize_ACK(routing_id_, tag, bounds.size()));
 }
 
+namespace {
+void OnSnapshotFailed(scoped_refptr<content::RenderWidget> render_widget,
+                      int routing_id) {
+  render_widget->Send(new ViewHostMsg_Snapshot(routing_id, false, SkBitmap()));
+}
+}  // namespace
+
+void RenderWidget::OnSnapshot(const gfx::Rect& src_subrect) {
+  base::TimeTicks beginning_time = base::TimeTicks::Now();
+
+  base::ScopedClosureRunner scoped_callback_runner(
+      base::Bind(OnSnapshotFailed, make_scoped_refptr(this), routing_id_));

[jamesr, 2013/03/22 00:05:33]

This functional style is highly uncommon in chromium and IMO overly complicated.
 If you want to make sure that some code happens if some of the intermediate
operations fail, move the operations that may fail to a helper function that
returns a bool and then deal with the response in the caller.

[justinlin, 2013/03/22 00:43:39]

Done.

+
+  SkBitmap snapshot;
+  if (!webwidget_ || src_subrect.IsEmpty())
+    return;
+
+  gfx::Rect viewport_size = gfx::IntersectRects(
+      src_subrect, gfx::Rect(physical_backing_size_));
+
+  skia::RefPtr<SkCanvas> canvas = skia::AdoptRef(
+      skia::CreatePlatformCanvas(viewport_size.width(),
+                                 viewport_size.height(),
+                                 true,
+                                 NULL,
+                                 skia::RETURN_NULL_ON_FAILURE));
+  if (!canvas.get())
+    return;
+
+  canvas->save();
+  webwidget_->layout();
+
+  PaintRect(viewport_size, viewport_size.origin(), canvas.get());
+  canvas->restore();
+
+  const SkBitmap& bitmap = skia::GetTopDevice(*canvas)->accessBitmap(false);
+  if (!bitmap.copyTo(&snapshot, SkBitmap::kARGB_8888_Config))
+    return;
+
+  UMA_HISTOGRAM_TIMES("Renderer4.Snapshot",
+                      base::TimeTicks::Now() - beginning_time);
+
+  scoped_callback_runner.Release();
+
+  Send(new ViewHostMsg_Snapshot(routing_id_, true, snapshot));
+}
+
 void RenderWidget::OnRepaint(const gfx::Size& size_to_paint) {
   // During shutdown we can just ignore this message.
   if (!webwidget_)