<webview>: Fix missing transparency in captureVisibleRegion().

extensions/browser/api/web_contents_capture_client.h

 // Copyright 2013 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.
 
 #ifndef EXTENSIONS_BROWSER_API_WEB_CONTENTS_CAPTURE_CLIENT_H_
 #define EXTENSIONS_BROWSER_API_WEB_CONTENTS_CAPTURE_CLIENT_H_
 
 #include "base/macros.h"
 #include "content/public/browser/readback_types.h"
 #include "extensions/browser/extension_function.h"
@@ skipping 10 matching lines @@
 // Base class for capturing visible area of a WebContents.
 // This is used by both webview.captureVisibleRegion and tabs.captureVisibleTab.
 class WebContentsCaptureClient {
  public:
   WebContentsCaptureClient() {}
 
  protected:
   virtual ~WebContentsCaptureClient() {}
 
   virtual bool IsScreenshotEnabled() = 0;
+  virtual bool ContentsHasTransparency() = 0;

[wjmaclean, 2016/04/06 12:39:21]

This name is a bit misleading, since it may return true even if the contents
doesn't have transparency (e.g. a WebView with allowsTransparency set, but
displaying content without transparency).

Perhaps "ClientAllowsTransparency"?

[avallee, 2016/04/06 14:12:27]

Done.

 
   enum FailureReason {
     FAILURE_REASON_UNKNOWN,
     FAILURE_REASON_ENCODING_FAILED,
     FAILURE_REASON_VIEW_INVISIBLE
   };
   bool CaptureAsync(content::WebContents* web_contents,
                     const api::extension_types::ImageDetails* image_detail,
                     const content::ReadbackRequestCallback callback);
   bool EncodeBitmap(const SkBitmap& bitmap, std::string* base64_result);
   virtual void OnCaptureFailure(FailureReason reason) = 0;
   virtual void OnCaptureSuccess(const SkBitmap& bitmap) = 0;
   void CopyFromBackingStoreComplete(const SkBitmap& bitmap,
                                     content::ReadbackResponse response);
 
  private:
   // The format (JPEG vs PNG) of the resulting image.  Set in RunAsync().
   api::extension_types::ImageFormat image_format_;
 
   // Quality setting to use when encoding jpegs.  Set in RunAsync().
   int image_quality_;
 
   DISALLOW_COPY_AND_ASSIGN(WebContentsCaptureClient);
 };
 
 }  // namespace extensions
 
 #endif  // EXTENSIONS_BROWSER_API_WEB_CONTENTS_CAPTURE_CLIENT_H_