Support having javascript return dictionaries.

ios/web/web_state/ui/web_view_js_utils.mm

Index: ios/web/web_state/ui/web_view_js_utils.mm
diff --git a/ios/web/web_state/ui/web_view_js_utils.mm b/ios/web/web_state/ui/web_view_js_utils.mm
index 48d65aac362036905e388e4e92a6f1bf3284afbb..78ce1d861694ff252cc6eaa73f6282b25d8e678e 100644
--- a/ios/web/web_state/ui/web_view_js_utils.mm
+++ b/ios/web/web_state/ui/web_view_js_utils.mm
@@ -9,6 +9,7 @@
 
 #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"
 
@@ -62,6 +63,16 @@ std::unique_ptr<base::Value> ValueResultFromWKResult(id wk_result) {
   } 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.
   }