Expose way to set google api key through CWVWebView class method.

ios/web_view/public/cwv_web_view.h

 // Copyright 2014 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 IOS_WEB_VIEW_PUBLIC_CWV_WEB_VIEW_H_
 #define IOS_WEB_VIEW_PUBLIC_CWV_WEB_VIEW_H_
 
 #import <UIKit/UIKit.h>
 
 // TODO(crbug.com/704946): Make framework style include work everywhere and
 // remove this #if.
@@ skipping 43 matching lines @@
 // The current page title.
 @property(nonatomic, readonly, copy) NSString* title;
 
 // Page loading progress from 0.0 to 1.0. KVO compliant.
 //
 // It is 0.0 initially before the first navigation starts. After a navigation
 // completes, it remains at 1.0 until a new navigation starts, at which point it
 // is reset to 0.0.
 @property(nonatomic, readonly) double estimatedProgress;
 
+// Use this method to set the necessary credentials used to communicate with
+// the Google API for features such as translate. See this link for more info:
+// https://support.google.com/googleapi/answer/6158857
+// This method must be called before any |CWVWebViews| are instantiated for
+// the keys to be used.
++ (void)setGoogleAPIKey:(NSString*)googleAPIKey
+               clientID:(NSString*)clientID
+           clientSecret:(NSString*)clientSecret;
+
 // |configuration| must not be null
 - (instancetype)initWithFrame:(CGRect)frame
                 configuration:(CWVWebViewConfiguration*)configuration
     NS_DESIGNATED_INITIALIZER;
 
 - (instancetype)initWithFrame:(CGRect)frame NS_UNAVAILABLE;
 - (instancetype)initWithCoder:(NSCoder*)aDecoder NS_UNAVAILABLE;
 
 // Navigates backwards or forwards by one page.  Does nothing if the
 // corresponding |canGoBack| or |canGoForward| method returns NO.
@@ skipping 11 matching lines @@
 - (void)loadRequest:(NSURLRequest*)request;
 
 // Evaluates a JavaScript string.
 // The completion handler is invoked when script evaluation completes.
 - (void)evaluateJavaScript:(NSString*)javaScriptString
          completionHandler:(void (^)(id, NSError*))completionHandler;
 
 @end
 
 #endif  // IOS_WEB_VIEW_PUBLIC_CWV_WEB_VIEW_H_