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

chrome/browser/extensions/api/tabs/tabs_api.h

 // Copyright (c) 2012 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 CHROME_BROWSER_EXTENSIONS_API_TABS_TABS_API_H_
 #define CHROME_BROWSER_EXTENSIONS_API_TABS_TABS_API_H_
 
 #include <string>
 #include <vector>
 
@@ skipping 199 matching lines @@
  protected:
   ~TabsCaptureVisibleTabFunction() override {}
 
  private:
   ChromeExtensionFunctionDetails chrome_details_;
 
   content::WebContents* GetWebContentsForID(int window_id);
 
   // extensions::WebContentsCaptureClient:
   bool IsScreenshotEnabled() override;
+  bool ClientAllowsTransparency() override;
   void OnCaptureSuccess(const SkBitmap& bitmap) override;
   void OnCaptureFailure(FailureReason reason) override;
 
   DECLARE_EXTENSION_FUNCTION("tabs.captureVisibleTab", TABS_CAPTUREVISIBLETAB)
 };
 
 // Implement API call tabs.executeScript and tabs.insertCSS.
 class ExecuteCodeInTabFunction : public ExecuteCodeFunction {
  public:
   ExecuteCodeInTabFunction();
@@ skipping 87 matching lines @@
   ~TabsGetZoomSettingsFunction() override {}
 
   bool RunAsync() override;
 
   DECLARE_EXTENSION_FUNCTION("tabs.getZoomSettings", TABS_GETZOOMSETTINGS)
 };
 
 }  // namespace extensions
 
 #endif  // CHROME_BROWSER_EXTENSIONS_API_TABS_TABS_API_H_