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

content/renderer/render_view_impl.cc

Index: content/renderer/render_view_impl.cc
diff --git a/content/renderer/render_view_impl.cc b/content/renderer/render_view_impl.cc
index 6578cd88cc32fd13c51f6a9b28eb23dc2ec6a2cd..7bdf278df97fc50af28fc2877cb3b22982d8e7cd 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -1116,6 +1116,7 @@ bool RenderViewImpl::OnMessageReceived(const IPC::Message& message) {
                         OnReleaseDisambiguationPopupDIB)
     IPC_MESSAGE_HANDLER(ViewMsg_WindowSnapshotCompleted,
                         OnWindowSnapshotCompleted)
+    IPC_MESSAGE_HANDLER(ViewMsg_Snapshot, OnSnapshot)
 
     // Have the super handle all other messages.
     IPC_MESSAGE_UNHANDLED(handled = RenderWidget::OnMessageReceived(message))
@@ -1899,6 +1900,55 @@ void RenderViewImpl::OnWindowSnapshotCompleted(const int snapshot_id,
   pending_snapshots_.erase(it);
 }
 
+namespace {
+
+bool CaptureSnapshot(WebView* view,
+                     const gfx::Rect& src_subrect,
+                     SkBitmap* snapshot) {
+  base::TimeTicks beginning_time = base::TimeTicks::Now();
+
+  view->layout();
+  const WebSize& size = view->size();

[jamesr, 2013/03/18 22:41:18]

I'm not sure about this - the size of a WebWidget is its logical size, not
physical pixel.  On a high DPI device these won't be the same.  I think you want
to be talking in terms of the device/physical pixels here and probably just want
to intersect with physical_backing_size_

[justinlin, 2013/03/18 23:27:51]

Done. Yea, this old stuff didn't really work with HiDPI. Fixed now.

+  gfx::Rect viewport_size = gfx::IntersectRects(
+      src_subrect, gfx::Rect(size.width, size.height));
+
+  skia::RefPtr<SkCanvas> canvas = skia::AdoptRef(
+      skia::CreatePlatformCanvas(viewport_size.width(),
+                                 viewport_size.height(),
+                                 true,
+                                 NULL,
+                                 skia::RETURN_NULL_ON_FAILURE));
+  if (!canvas)
+    return false;
+
+  view->paint(webkit_glue::ToWebCanvas(canvas.get()), viewport_size);
+
+  const SkBitmap& bitmap = skia::GetTopDevice(*canvas)->accessBitmap(false);
+  if (!bitmap.copyTo(snapshot, SkBitmap::kARGB_8888_Config))
+    return false;
+
+  UMA_HISTOGRAM_TIMES("Renderer4.Snapshot",
+                      base::TimeTicks::Now() - beginning_time);
+  return true;
+}
+
+}  // namespace
+
+void RenderViewImpl::OnSnapshot(const gfx::Rect& src_subrect) {
+  SkBitmap snapshot;
+  bool error = false;
+
+  if (!webview()->mainFrame() || !CaptureSnapshot(webview(),
+                                                  src_subrect,
+                                                  &snapshot))
+    error = true;
+
+  DCHECK(error == snapshot.empty()) <<
+      "Snapshot should be empty on error, non-empty otherwise.";
+
+  Send(new ViewHostMsg_Snapshot(routing_id_, !error, snapshot));
+}
+
 // WebKit::WebViewClient ------------------------------------------------------
 
 WebView* RenderViewImpl::createView(