[ios] Added API to enable/disable web usage for WebState.

ios/web/public/test/test_web_state.h

Index: ios/web/public/test/test_web_state.h
diff --git a/ios/web/public/test/test_web_state.h b/ios/web/public/test/test_web_state.h
index 540df722d639c02c747b74c172a89ae42b9c705d..ccefebcc03b3a840c8a5d535d2fd49231b6f72c4 100644
--- a/ios/web/public/test/test_web_state.h
+++ b/ios/web/public/test/test_web_state.h
@@ -23,9 +23,11 @@ class TestWebState : public WebState {
   ~TestWebState() override;
 
   // WebState implementation.
-  UIView* GetView() override;
   WebStateDelegate* GetDelegate() override;
   void SetDelegate(WebStateDelegate* delegate) override;
+  bool IsWebUsageEnabled() const override;
+  void SetWebUsageEnabled(bool enabled) override;
+  UIView* GetView() override;
   BrowserState* GetBrowserState() const override;
   void OpenURL(const OpenURLParams& params) override {}
   NavigationManager* GetNavigationManager() override;
@@ -68,6 +70,7 @@ class TestWebState : public WebState {
   void SetTrustLevel(URLVerificationTrustLevel trust_level);
 
  private:
+  bool web_usage_enabled_;
   GURL url_;
   base::string16 title_;
   URLVerificationTrustLevel trust_level_;