Only send autofill JS on visible webStates.

When autofilling credit card, the CVC prompt View disables
the webState.
JS processing may be different when view is not visible. This
makes some sites like walgreens.com flaky.
This CL queue the JS if the webState is not visible and executes
it after |webStateWasShown| is called.

Bug: 728606
Change-Id: I7a9ffd5e15d403a7faf9f7f4f4151371474676d5
Reviewed-on: https://chromium-review.googlesource.com/817277
Commit-Queue: Olivier Robin <olivierrobin@chromium.org>
Reviewed-by: Moe Ahmadi <mahmadi@chromium.org>
Reviewed-by: Peter Lee <pkl@chromium.org>
Cr-Commit-Position: refs/heads/master@{#524354}

components/autofill/ios/browser/autofill_agent.mm

@@ -149,6 +149,10 @@ void GetFormAndField(autofill::FormData* form,
 // key/value suggestions if the user hasn't started typing.
 - (NSArray*)processSuggestions:(NSArray*)suggestions;
 
+// Sends the the |formData| to the JavaScript manager of |webState_| to actually
+// fill the data.
+- (void)sendDataToWebState:(NSString*)formData;
+
 @end
 
 @implementation AutofillAgent {
@@ -192,6 +196,8 @@ void GetFormAndField(autofill::FormData* form,
   // The reference is weak because a weak pointer is sent to our
   // AutofillManagerDelegate.
   base::WeakPtr<autofill::AutofillPopupDelegate> popupDelegate_;
+  // The autofill data that needs to be send when the |webState_| is shown.
+  NSString* pendingFormData_;
 }
 
 - (instancetype)initWithPrefService:(PrefService*)prefService
@@ -651,6 +657,14 @@ void GetFormAndField(autofill::FormData* form,
   [self detachFromWebState];
 }
 
+- (void)webStateWasShown:(web::WebState*)webState {
+  DCHECK_EQ(webState_, webState);
+  if (pendingFormData_) {
+    [self sendDataToWebState:pendingFormData_];
+  }
+  pendingFormData_ = nil;
+}
+
 - (void)webState:(web::WebState*)webState
     didSubmitDocumentWithFormNamed:(const std::string&)formName
                      userInitiated:(BOOL)userInitiated
@@ -877,14 +891,24 @@ void GetFormAndField(autofill::FormData* form,
   // Stringify the JSON data and send it to the UIWebView-side fillForm method.
   std::string dataString;
   base::JSONWriter::Write(*formData.get(), &dataString);
+  NSString* nsDataString = base::SysUTF8ToNSString(dataString);
+
+  if (!webState_->IsVisible()) {
+    pendingFormData_ = nsDataString;
+    return;
+  }
+  [self sendDataToWebState:nsDataString];
+}
 
+- (void)sendDataToWebState:(NSString*)formData {
+  DCHECK(webState_->IsVisible());
   // It is possible that the fill was not initiated by selecting a suggestion.
   // In this case we provide an empty callback.
   if (!suggestionHandledCompletion_)
     suggestionHandledCompletion_ = [^{
     } copy];
   [jsAutofillManager_
-                fillForm:base::SysUTF8ToNSString(dataString)
+                fillForm:formData
       forceFillFieldName:base::SysUTF16ToNSString(pendingAutocompleteField_)
        completionHandler:suggestionHandledCompletion_];
   suggestionHandledCompletion_ = nil;