Expose the capturePicture feature in RenderView for Android WebView legacy API support.

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 d2b9103753568d8f999c49beca4f585786c57ef5..f0191a593af1e43e9c211fda367d89b7348c17a0 100644
--- a/content/renderer/render_view_impl.cc
+++ b/content/renderer/render_view_impl.cc
@@ -6578,4 +6578,26 @@ void RenderViewImpl::OnReleaseDisambiguationPopupDIB(
   RenderProcess::current()->ReleaseTransportDIB(dib);
 }
 
+#if defined(OS_ANDROID)
+void RenderViewImpl::SetCapturePictureCallback(
+    const CapturePictureCallback& callback) {
+  if (CommandLine::ForCurrentProcess()->HasSwitch(
+      switches::kEnableWebViewCapturePictureAPI))
+    capture_picture_callback_ = callback;
+}
+
+skia::RefPtr<SkPicture> RenderViewImpl::CapturePicture() {
+  return web_layer_tree_view_ && CommandLine::ForCurrentProcess()->HasSwitch(

[Leandro Graciá Gil, 2013/01/11 13:11:33]

This patch depends on https://codereview.chromium.org/11575049/ landing
successfully and introducing web_layer_tree_view_ in RenderWidget.

+      switches::kEnableWebViewCapturePictureAPI) ?
+          web_layer_tree_view_->capturePicture() :
+          skia::RefPtr<SkPicture>();
+}
+
+void RenderViewImpl::didBecomeReadyForAdditionalInput() {

[joth, 2013/01/11 21:41:17]

I propose we should separate out the two different primitives here, and extract
upwards a lot of the policy decisions into the embedder and out of content/ as a
result:

1/ Here, we just push  a new notification to RV observers:-
FOR_EACH_OBSERVER(RenderViewObserver, observers_,
DidBecomeReadyForAdditionalInput();
i.e. this can be done unconditionally, regardless of OS_ANDROID or any funky
command line switch.

2/ We add the RenderViewImpl::CapturePicture() as you have it above, but as it's
not (of itself) spontaneous doing anything at all I'd argue a command line
switch is not needed. Just a warning on the function that it's not necessarily
"free" to call, and perhaps we also keep it under OS_ANDROID.

3/ The RenderViewImpl::SetCapturePictureCallback can be removed entirely. We
just implement that logic (receiving DidBecomeReadyForAdditionalInput
notifications and calling CapturePicture() if appropriate) up in the
anroid_webview layer.

[jamesr, 2013/01/11 21:53:26]

why are you hooking on didBecomeReadyForAdditionalInput()? this operation
doesn't have anything to do with input event throttling

[Leandro Graciá Gil, 2013/01/12 00:26:09]

The intention is to trigger the callback on every new frame contents. This is
supposed to be called on didCommit by the WebKit side, isn't it? That's what
enne and nduca suggested us (if I interpreted it right).

Following Joth's suggestion, is there anything that we could use already exposed
to RenderViewObservers?

+  RenderWidget::didBecomeReadyForAdditionalInput();
+  if (web_layer_tree_view_ && !capture_picture_callback_.is_null())
+      capture_picture_callback_.Run(web_layer_tree_view_->capturePicture());
+}
+#endif
+
 }  // namespace content