Fix a crash when saving a <canvas> or <img> image which is large.

content/browser/renderer_host/render_message_filter.cc

Index: content/browser/renderer_host/render_message_filter.cc
diff --git a/content/browser/renderer_host/render_message_filter.cc b/content/browser/renderer_host/render_message_filter.cc
index 13ce2f81908143bf29cb00cdc31c5c8253c351a2..656f56aeb9db5e89281b4dcbee41a757f5665a9e 100644
--- a/content/browser/renderer_host/render_message_filter.cc
+++ b/content/browser/renderer_host/render_message_filter.cc
@@ -391,6 +391,8 @@ bool RenderMessageFilter::OnMessageReceived(const IPC::Message& message) {
     IPC_MESSAGE_HANDLER_DELAY_REPLY(ViewHostMsg_LoadFont, OnLoadFont)
 #endif
     IPC_MESSAGE_HANDLER(ViewHostMsg_DownloadUrl, OnDownloadUrl)
+    IPC_MESSAGE_HANDLER(ViewHostMsg_SaveImageFromDataURL,
+                        OnSaveImageFromDataURL)
 #if defined(ENABLE_PLUGINS)
     IPC_MESSAGE_HANDLER_DELAY_REPLY(ViewHostMsg_GetPlugins, OnGetPlugins)
     IPC_MESSAGE_HANDLER(FrameHostMsg_GetPluginInfo, OnGetPluginInfo)
@@ -860,11 +862,11 @@ void RenderMessageFilter::OnGetMonitorColorProfile(std::vector<char>* profile) {
 }
 #endif
 
-void RenderMessageFilter::OnDownloadUrl(int render_view_id,
-                                        const GURL& url,
-                                        const Referrer& referrer,
-                                        const base::string16& suggested_name,
-                                        const bool use_prompt) {
+void RenderMessageFilter::DownloadUrl(int render_view_id,
+                                      const GURL& url,
+                                      const Referrer& referrer,
+                                      const base::string16& suggested_name,
+                                      const bool use_prompt) {
   scoped_ptr<DownloadSaveInfo> save_info(new DownloadSaveInfo());
   save_info->suggested_name = suggested_name;
   save_info->prompt_for_save_location = use_prompt;
@@ -893,6 +895,23 @@ void RenderMessageFilter::OnDownloadUrl(int render_view_id,
       ResourceDispatcherHostImpl::DownloadStartedCallback());
 }
 
+void RenderMessageFilter::OnDownloadUrl(int render_view_id,
+                                        const GURL& url,
+                                        const Referrer& referrer,
+                                        const base::string16& suggested_name) {
+  DownloadUrl(render_view_id, url, referrer, suggested_name);
+}
+
+void RenderMessageFilter::OnSaveImageFromDataURL(int render_view_id,
+                                                 const std::string& data_url) {
+  // Note: |data_url| has a size limitation. (< 10MB)
+  // Please refer to RenderViewImpl::saveImageFromDataURL().
+  const int MAX_LENGTH_OF_DATA_URL = 1024 * 1024 * 10;

[palmer, 2014/09/02 17:58:04]

This should be a size_t. Note that you are comparing it with a size_t
(std::string::length returns size_t). You might even get a compiler warning
about comparing signed with unsigned; declaring |MAX_LENGTH_OF_DATA_URL| as
size_t will fix that.

I still think it would be a good idea to check this limit on the renderer side,
too — not as a security mechanism, but as an optimization for not even trying to
send messages that the browser would reject.

If you do that, you'll need to put this declaration in a place that both pieces
of code can #include, to keep the policy consistent.

[zino, 2014/09/03 01:45:58]

A stupid mistake. :-P
Done.
I agree with you.
So, I've just removed the check logic on the browser side.
(You don't think we need double checks, do you?)

+  if (data_url.length() < MAX_LENGTH_OF_DATA_URL)
+    DownloadUrl(render_view_id, GURL(data_url),
+        Referrer(), base::string16(), true);
+}
+
 void RenderMessageFilter::OnCheckNotificationPermission(
     const GURL& source_origin, int* result) {
 #if defined(ENABLE_NOTIFICATIONS)