Support having javascript return dictionaries.

ios/web/web_state/ui/web_view_js_utils.mm

 // 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.
 
 #import "ios/web/web_state/ui/web_view_js_utils.h"
 
 #include <CoreFoundation/CoreFoundation.h>
 #import <WebKit/WebKit.h>
 
 #include "base/logging.h"
 #include "base/mac/scoped_nsobject.h"
+#include "base/memory/ptr_util.h"
 #include "base/strings/sys_string_conversions.h"
 #include "base/values.h"
 
 namespace {
 
 // Converts result of WKWebView script evaluation to a string.
 NSString* StringResultFromWKResult(id result) {
   if (!result)
     return @"";
 
@@ skipping 33 matching lines @@
   } else if (result_type == CFNumberGetTypeID()) {
     result.reset(new base::FundamentalValue([wk_result doubleValue]));
     DCHECK(result->IsType(base::Value::TYPE_DOUBLE));
   } else if (result_type == CFBooleanGetTypeID()) {
     result.reset(
         new base::FundamentalValue(static_cast<bool>([wk_result boolValue])));
     DCHECK(result->IsType(base::Value::TYPE_BOOLEAN));
   } else if (result_type == CFNullGetTypeID()) {
     result = base::Value::CreateNullValue();
     DCHECK(result->IsType(base::Value::TYPE_NULL));
+  } else if (result_type == CFDictionaryGetTypeID()) {
+    std::unique_ptr<base::DictionaryValue> dictionary =
+        base::MakeUnique<base::DictionaryValue>();
+    for (id key in wk_result) {
+      DCHECK([key respondsToSelector:@selector(UTF8String)]);
+      const std::string& path([key UTF8String]);

[Eugene But (OOO till 7-30), 2016/09/09 15:26:21]

Please use sys_string_conversions instead of |UTF8String|.

[jif-google, 2016/09/09 17:54:45]

Acknowledged.

[Eugene But (OOO till 7-30), 2016/09/09 18:28:57]

[key UTF8String] may return nil, which will crash the app. Using
sys_string_conversions is not just nice to have thing, it's a question of
correctness.

+      dictionary->Set(path,
+                      ValueResultFromWKResult([wk_result objectForKey:key]));

[Eugene But (OOO till 7-30), 2016/09/09 15:26:21]

This JSON is coming from internet, which means that it can be almost infinitely
deep and cause stack overflow.

[jif-google, 2016/09/09 17:54:45]

When does the JSON come from the internet?

[Eugene But (OOO till 7-30), 2016/09/09 18:28:57]

wk_result is the result of script evaluation, for example a result of __crWeb
function call. Web pages can easily override those calls and provide a
dictionary which can overflow the stack.

+    }
+    result = std::move(dictionary);
   } else {
     NOTREACHED();  // Convert other types as needed.
   }
   return result;
 }
 
 void EvaluateJavaScript(WKWebView* web_view,
                         NSString* script,
                         JavaScriptCompletion completion_handler) {
   void (^web_view_completion_handler)(id, NSError*) = nil;
@@ skipping 24 matching lines @@
                 userInfo:@{NSLocalizedDescriptionKey : error_message}]);
       completion_handler(nil, error);
     });
     return;
   }
 
   [web_view evaluateJavaScript:script completionHandler:completion_handler];
 }
 
 }  // namespace web