Implement webview.captureVisibleRegion()

This CL implements  webview.captureVisibleRegion(), an extension/apps
API to allow WebView users to capture screenshots of the contents
displayed in a WebView. The surfaces contents capture has been plumbed
via RenderWidgetHostViewChildFrame so this implementation should not
require changes when WebView switches to using OOPIF.

As part of the implementation, there are two notable refactors:

1) CaptureWebContentsFunction has been refactored into
WebContentsCaptureClient to remove the extensions::AsyncExtensionFunction
dependence so that this code can be used by both tabs.captureVisibleTab
and webview.captureVisibleRegion, and

2) common code from DelegatedFrameHost has ben moved to
content/browser/compositor/surface_utils.* in order to avoid duplication
as both DelegatedFrameHost and RenderWidgetHostViewChildFrame now
use the code.

Finally, this CL adds a surface-drawn callback to
RenderWidgetHostViewChildFrame, to allow deferring a
screen capture request until a frame has actually been
drawn. This callback can be used to simplify some
existing tests.

BUG=326755
CQ_INCLUDE_TRYBOTS=tryserver.chromium.linux:linux_site_isolation

Review URL: https://codereview.chromium.org/1635513003

Cr-Commit-Position: refs/heads/master@{#372799}

3 files changed, 34 insertions, 0 deletions

diff --git a/extensions/renderer/resources/extensions_renderer_resources.grd b/extensions/renderer/resources/extensions_renderer_resources.grd
index bad8e29..b4f5dad 100644
--- a/extensions/renderer/resources/extensions_renderer_resources.grd
+++ b/extensions/renderer/resources/extensions_renderer_resources.grd
@@ -61,6 +61,7 @@
       <include name="IDR_WEB_VIEW_ATTRIBUTES_JS" file="guest_view/web_view/web_view_attributes.js" type="BINDATA" />
       <include name="IDR_WEB_VIEW_CONSTANTS_JS" file="guest_view/web_view/web_view_constants.js" type="BINDATA" />
       <include name="IDR_WEB_VIEW_EVENTS_JS" file="guest_view/web_view/web_view_events.js" type="BINDATA" />
+      <include name="IDR_WEB_VIEW_EXPERIMENTAL_JS" file="guest_view/web_view/web_view_experimental.js" type="BINDATA" />
       <include name="IDR_WEB_VIEW_IFRAME_JS" file="guest_view/web_view/web_view_iframe.js" type="BINDATA" />
       <include name="IDR_WEB_VIEW_INTERNAL_CUSTOM_BINDINGS_JS" file="guest_view/web_view/web_view_internal.js" type="BINDATA" />
       <include name="IDR_WEB_VIEW_JS" file="guest_view/web_view/web_view.js" type="BINDATA" />
diff --git a/extensions/renderer/resources/guest_view/web_view/web_view.js b/extensions/renderer/resources/guest_view/web_view/web_view.js
index 6dd4fae..b5d08c1 100644
--- a/extensions/renderer/resources/guest_view/web_view/web_view.js
+++ b/extensions/renderer/resources/guest_view/web_view/web_view.js
@@ -31,6 +31,10 @@ WebViewImpl.setupElement = function(proto) {
   // Public-facing API methods.
   var apiMethods = WebViewImpl.getApiMethods();
 
+  // Add the experimental API methods, if available.
+  var experimentalApiMethods = WebViewImpl.maybeGetExperimentalApiMethods();
+  apiMethods = $Array.concat(apiMethods, experimentalApiMethods);
+
   // Create default implementations for undefined API methods.
   var createDefaultApiMethod = function(m) {
     return function(var_args) {
@@ -220,6 +224,11 @@ WebViewImpl.prototype.makeElementFullscreen = function() {
 // Implemented when the ChromeWebView API is available.
 WebViewImpl.prototype.maybeSetupContextMenus = function() {};
 
+// Implemented when the experimental WebView API is available.
+WebViewImpl.maybeGetExperimentalApiMethods = function() {
+  return [];
+};
+
 GuestViewContainer.registerElement(WebViewImpl);
 
 // Exports.
diff --git a/extensions/renderer/resources/guest_view/web_view/web_view_experimental.js b/extensions/renderer/resources/guest_view/web_view/web_view_experimental.js
new file mode 100644
index 0000000..96331df
--- /dev/null
+++ b/extensions/renderer/resources/guest_view/web_view/web_view_experimental.js
@@ -0,0 +1,24 @@
+// Copyright 2015 The Chromium Authors. All rights reserved.
+// Use of this source code is governed by a BSD-style license that can be
+// found in the LICENSE file.
+
+// This module implements experimental API for <webview>.
+// See web_view.js and web_view_api_methods.js for details.
+//
+// <webview> Experimental API is only available on canary and channels of
+// Chrome.
+
+var WebViewImpl = require('webView').WebViewImpl;
+var WebViewInternal = require('webViewInternal').WebViewInternal;
+
+// An array of <webview>'s experimental API methods.  See |WEB_VIEW_API_METHODS|
+// in web_view_api_methods.js for more details.
+var WEB_VIEW_EXPERIMENTAL_API_METHODS = [
+  // Captures the visible region of the WebView contents into a bitmap.
+  'captureVisibleRegion'
+];
+
+// Registers the experimantal WebVIew API when available.
+WebViewImpl.maybeGetExperimentalApiMethods = function() {
+  return WEB_VIEW_EXPERIMENTAL_API_METHODS;
+};