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

content/common/view_messages.h

Index: content/common/view_messages.h
diff --git a/content/common/view_messages.h b/content/common/view_messages.h
index 761e62d8e62d4a92aa94431776103b635d6bf071..ead06f75b3770311689afa612159b4090938cbd2 100644
--- a/content/common/view_messages.h
+++ b/content/common/view_messages.h
@@ -1207,12 +1207,11 @@ IPC_MESSAGE_ROUTED2(ViewHostMsg_AppCacheAccessed,
                     bool /* blocked by policy */)
 
 // Initiates a download based on user actions like 'ALT+click'.
-IPC_MESSAGE_CONTROL5(ViewHostMsg_DownloadUrl,
+IPC_MESSAGE_CONTROL4(ViewHostMsg_DownloadUrl,
                      int /* render_view_id */,
                      GURL /* url */,
                      content::Referrer /* referrer */,
-                     base::string16 /* suggested_name */,
-                     bool /* use prompt for save location */)
+                     base::string16 /* suggested_name */)
 
 // Used to go to the session history entry at the given offset (ie, -1 will
 // return the "back" item).
@@ -1352,6 +1351,13 @@ IPC_MESSAGE_ROUTED2(ViewHostMsg_EnumerateDirectory,
                     int /* request_id */,
                     base::FilePath /* file_path */)
 
+// Asks the browser to save a image (for <canvas> or <img>) from a data URL.
+// Note: |data_url| is the contents of a data:URL, and that it's represented as
+// a string only to work around size limitations for GURLs in IPC messages.
+IPC_MESSAGE_CONTROL2(ViewHostMsg_SaveImageFromDataURL,
+                     int /* render_view_id */,
+                     std::string /* data_url */)
+
 // Tells the browser to move the focus to the next (previous if reverse is
 // true) focusable element.
 IPC_MESSAGE_ROUTED1(ViewHostMsg_TakeFocus,