Fixed thread-unsafe use of gfx::Image in app shortcut creation.

chrome/browser/web_applications/web_app.h

Index: chrome/browser/web_applications/web_app.h
diff --git a/chrome/browser/web_applications/web_app.h b/chrome/browser/web_applications/web_app.h
index a7d93fbeea64e1884a80acf54b894747ef0f496c..72f728cb5da60d5eb839ec883c10c5dde7879d36 100644
--- a/chrome/browser/web_applications/web_app.h
+++ b/chrome/browser/web_applications/web_app.h
@@ -10,6 +10,7 @@
 
 #include "base/callback.h"
 #include "base/files/file_path.h"
+#include "base/memory/scoped_ptr.h"
 #include "base/strings/string16.h"
 #include "build/build_config.h"
 #include "chrome/browser/shell_integration.h"
@@ -53,6 +54,12 @@ struct ShortcutInfo {
   base::FilePath profile_path;
   std::string profile_name;
   std::string version_for_display;
+
+ private:
+  // ShortcutInfo must not be copied; generally it is passed around via
+  // scoped_ptrs. This is to allow passing ShortcutInfos between threads,
+  // despite ImageFamily having a non-thread-safe reference count.

[msw, 2015/04/01 16:23:00]

Hmm, tough spot, but I suppose a thread-safe gfx::Image[Family] isn't a simple
matter, can you link to the chromium-dev thread you mention?

[Matt Giuca, 2015/04/01 22:52:17]

https://groups.google.com/a/chromium.org/d/msg/chromium-dev/8LqVoXQ_2bo/cW0tH...

Yeah, believe me. I've made about 3 or 4 alternative CLs to fix this issue in
various ways. This was the least awful.

Making gfx::Image thread-safe I did here:
https://codereview.chromium.org/240293006/
and discussed that on the above thread. It wasn't well received. Basically
people didn't like the idea of unnecessarily making something thread-safe
universally when it was possible to just ensure it is only accessed on a single
thread.

I think having non-copyable classes is generally considered better practice
anyhow.

+  DISALLOW_COPY_AND_ASSIGN(ShortcutInfo);
 };
 
 // This specifies a folder in the system applications menu (e.g the Start Menu
@@ -98,16 +105,16 @@ enum ShortcutCreationReason {
 };
 
 // Called by GetInfoForApp after fetching the ShortcutInfo and FileHandlersInfo.
-typedef base::Callback<void(const ShortcutInfo&,
+typedef base::Callback<void(scoped_ptr<ShortcutInfo>,
                             const extensions::FileHandlersInfo&)> InfoCallback;
 
 // Called by GetShortcutInfoForApp after fetching the ShortcutInfo.
-typedef base::Callback<void(const ShortcutInfo&)> ShortcutInfoCallback;
+typedef base::Callback<void(scoped_ptr<ShortcutInfo>)> ShortcutInfoCallback;
 
 #if defined(TOOLKIT_VIEWS)
 // Extracts shortcut info of the given WebContents.
-void GetShortcutInfoForTab(content::WebContents* web_contents,
-                           ShortcutInfo* info);
+scoped_ptr<ShortcutInfo> GetShortcutInfoForTab(
+    content::WebContents* web_contents);
 #endif
 
 // Updates web app shortcut of the WebContents. This function checks and
@@ -117,7 +124,7 @@ void GetShortcutInfoForTab(content::WebContents* web_contents,
 // updates (recreates) them if they exits.
 void UpdateShortcutForTabContents(content::WebContents* web_contents);
 
-ShortcutInfo ShortcutInfoForExtensionAndProfile(
+scoped_ptr<ShortcutInfo> ShortcutInfoForExtensionAndProfile(
     const extensions::Extension* app,
     Profile* profile);
 
@@ -173,13 +180,13 @@ std::string GetExtensionIdFromApplicationName(const std::string& app_name);
 void CreateShortcutsWithInfo(
     ShortcutCreationReason reason,
     const ShortcutLocations& locations,
-    const ShortcutInfo& shortcut_info,
+    scoped_ptr<ShortcutInfo> shortcut_info,
     const extensions::FileHandlersInfo& file_handlers_info);
 
 // Currently only called by app_list_service_mac to create a shim for the
 // app launcher.
 void CreateNonAppShortcut(const ShortcutLocations& locations,
-                          const ShortcutInfo& shortcut_info);
+                          scoped_ptr<ShortcutInfo> shortcut_info);
 
 // Creates shortcuts for an app. This loads the app's icon from disk, and calls
 // CreateShortcutsWithInfo(). If you already have a ShortcutInfo with the app's
@@ -239,7 +246,7 @@ std::vector<base::FilePath> GetShortcutPaths(
 // |creation_locations| contains information about where to create them.
 bool CreatePlatformShortcuts(
     const base::FilePath& shortcut_data_path,
-    const ShortcutInfo& shortcut_info,
+    scoped_ptr<ShortcutInfo> shortcut_info,
     const extensions::FileHandlersInfo& file_handlers_info,
     const ShortcutLocations& creation_locations,
     ShortcutCreationReason creation_reason);
@@ -248,7 +255,7 @@ bool CreatePlatformShortcuts(
 // platform specific implementation of the DeleteAllShortcuts function, and
 // is executed on the FILE thread.
 void DeletePlatformShortcuts(const base::FilePath& shortcut_data_path,
-                             const ShortcutInfo& shortcut_info);
+                             scoped_ptr<ShortcutInfo> shortcut_info);
 
 // Updates all the shortcuts we have added for this extension. This is the
 // platform specific implementation of the UpdateAllShortcuts function, and
@@ -256,7 +263,7 @@ void DeletePlatformShortcuts(const base::FilePath& shortcut_data_path,
 void UpdatePlatformShortcuts(
     const base::FilePath& shortcut_data_path,
     const base::string16& old_app_title,
-    const ShortcutInfo& shortcut_info,
+    scoped_ptr<ShortcutInfo> shortcut_info,
     const extensions::FileHandlersInfo& file_handlers_info);
 
 // Delete all the shortcuts for an entire profile.