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

content/public/renderer/render_view.h

Index: content/public/renderer/render_view.h
diff --git a/content/public/renderer/render_view.h b/content/public/renderer/render_view.h
index 5cf2af9083b7b5e8a8000cd2e5b9dd228b89585f..24931e6ccde2c17acff05bdba55cd30b5420bde1 100644
--- a/content/public/renderer/render_view.h
+++ b/content/public/renderer/render_view.h
@@ -9,8 +9,10 @@
 #include "base/string16.h"
 #include "content/common/content_export.h"
 #include "ipc/ipc_sender.h"
+#include "skia/ext/refptr.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebNavigationPolicy.h"
 #include "third_party/WebKit/Source/WebKit/chromium/public/WebPageVisibilityState.h"
+#include "third_party/skia/include/core/SkPicture.h"

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

please don't include this header just to have references to
skia::RefPtr<SkPictures> - a forward declaration should suffice

[Leandro Graciá Gil, 2013/01/15 20:46:11]

Done.

 #include "ui/gfx/native_widget_types.h"
 
 namespace webkit_glue {
@@ -163,6 +165,23 @@ class CONTENT_EXPORT RenderView : public IPC::Sender {
   // Returns a collection of security info about |frame|.
   virtual SSLStatus GetSSLStatusOfFrame(WebKit::WebFrame* frame) const = 0;
 
+#if defined(OS_ANDROID)
+  typedef base::Callback<void(skia::RefPtr<SkPicture>)> CapturePictureCallback;
+
+  // Sets a callback to receive a new SkPicture with the contents of every new

[Jói, 2013/01/11 18:40:08]

Can there be exactly 0 or 1 callback, or can there be multiple?

Also, would like to see more of the documentation from your comment added to the
documentation that goes into the file here, i.e. why this is Android-only and
why it's guarded by a command-line flag.

[Leandro Graciá Gil, 2013/01/15 20:46:11]

Removing and implementing via RenderViewObserver.

+  // frame as part of the legacy Android WebView capture picture API.
+  // Should not be used for any other purposes for performance reasons.
+  // Requires the kEnableWebViewCapturePictureAPI command line switch to be set.
+  virtual void SetCapturePictureCallback(

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

Some extra context here. We need to support both the renderer calling us back on
new frame contents (WebView.PictureListener.onNewPicture) and we explicitly
requesting the current contents (WebView.capturePicture). The last is a
synchronous API which will require a synchronous IPC in the Android WebView
code. I suggest providing the picture also in the callback case (not just
notifying about a new one being available) in order to reduce the number of such
synchronous IPC calls.

Getting the SkPicture is a non-trivial task with a very good chance of having a
performance impact. We need to do this for legacy WebView API support, but this
approach should not be used by anyone else as it implies (or will imply in the
future) playing back the drawing commands of every single layer in the full
frame. Because of this I'm proposing these methods to be Android-only and
guarded by a command line flag. I'm open to any other approaches.

+      const CapturePictureCallback& callback) = 0;
+
+  // Returns a SkPicture with the full contents of the current frame as part of
+  // the legacy Android WebView capture picture API.
+  // Should not be used for any other purposes for performance reasons.
+  // Requires the kEnableWebViewCapturePictureAPI command line switch to be set.
+  virtual skia::RefPtr<SkPicture> CapturePicture() = 0;
+#endif
+
  protected:
   virtual ~RenderView() {}
 };