Hook up Chrome's wallpaper picker for mash.

chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc

Index: chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
diff --git a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
index eac4ab8f45341ff25769a07253a02f001113e7dc..5d29c2e82881b179393750a51ba6ddc46c7b8362 100644
--- a/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
+++ b/chrome/browser/chromeos/login/users/wallpaper/wallpaper_manager.cc
@@ -36,6 +36,7 @@
 #include "chrome/browser/chromeos/login/startup_utils.h"
 #include "chrome/browser/chromeos/login/wizard_controller.h"
 #include "chrome/browser/chromeos/settings/cros_settings.h"
+#include "chrome/browser/ui/ash/ash_util.h"
 #include "chrome/common/chrome_paths.h"
 #include "chrome/common/chrome_switches.h"
 #include "chrome/common/pref_names.h"
@@ -57,11 +58,18 @@
 #include "content/public/browser/browser_thread.h"
 #include "content/public/browser/notification_service.h"
 #include "content/public/common/content_switches.h"
+#include "content/public/common/mojo_shell_connection.h"
+#include "services/shell/public/cpp/connector.h"
+#include "skia/public/type_converters.h"
 #include "third_party/skia/include/core/SkColor.h"
 #include "ui/gfx/codec/jpeg_codec.h"
 #include "ui/gfx/image/image_skia_operations.h"
 #include "ui/gfx/skia_util.h"
 
+#if defined(MOJO_SHELL_CLIENT)
+#include "ash/mus/public/interfaces/wallpaper.mojom.h"
+#endif
+
 using content::BrowserThread;
 using wallpaper::WallpaperManagerBase;
 using wallpaper::WallpaperInfo;
@@ -172,6 +180,29 @@ void SetKnownUserWallpaperFilesId(
                                           wallpaper_files_id.id());
 }
 
+// A helper to set the wallpaper image for Ash and Mash.
+void SetWallpaper(const gfx::ImageSkia& image,
+                  wallpaper::WallpaperLayout layout) {
+#if defined(MOJO_SHELL_CLIENT)
+  if (chrome::IsRunningInMash()) {
+    shell::Connector* connector =
+        content::MojoShellConnection::Get()->GetConnector();
+    ash::mus::mojom::WallpaperControllerPtr wallpaper_controller;
+    connector->ConnectToInterface("mojo:ash_sysui", &wallpaper_controller);
+    wallpaper_controller->SetWallpaper(
+        skia::mojom::Bitmap::From(*image.bitmap()),

[dcheng, 2016/05/24 18:53:37]

Can we do this with a StructTraits instead? My worry about adding further
dependencies on the existing TypeConverter is that it's going to make it harder
to remove down the road.

[msw, 2016/05/24 22:06:37]

Yeah, Yuzhu gave me an intro to StructTraits, and it definitely seems possible.
Since I'm not adding a new type converter, but just making use of an existing
one, I wonder if it's necessary for this CL. Would you like me to add struct
traits and remove all existing skia bitmap type conversion uses and the
converter itself: (1) separately as a prerequisite to this CL, (2) done as part
of this CL (I hope not) or (3) left for a follow-up change?

[dcheng, 2016/05/25 17:31:26]

We can add the StructTraits without removing all uses of the old one in this CL,
I think. That way, we can start incremental migration over.

[msw, 2016/05/25 18:16:41]

I'd rather not pollute this wallpaper CL with the addition of skia bitmap
StructTraits. I'll put this CL on hold and implement that in a separate
prerequisite CL if you think it's a blocker.

[dcheng, 2016/05/25 19:56:40]

I'd strongly prefer to see that. I thought it'd be easier since this CL would be
defacto proof that the StructTraits works, but if you feel it would be better in
a separate CL, that's fine with me.

+        static_cast<ash::mus::mojom::WallpaperLayout>(layout));

[dcheng, 2016/05/24 18:53:37]

Similarly, do StructTraits work for enums yet?

[yzshen1, 2016/05/24 22:04:42]

Yes. For example:

module mojom;
enum SomeEnum {};
struct Foo {
  SomeEnum value;
};

The struct traits will be:

template<>
class StructTraits<mojom::Foo, CustomFoo> {
  // The getter of an enum field needs to return the exact mojo enum type.
  static mojom::SomeEnum value(const CustomFoo& input) {
    ...
  }
};

[msw, 2016/05/24 22:06:37]

We can support enums within a struct, but I don't think we have EnumTraits or
similar, let me know if there's some other approach you suggest.

[msw, 2016/05/24 22:06:37]

Right, but in this case, I'm passing an enum value to a mojom function, not
encapsulating it within a struct...

[dcheng, 2016/05/25 19:56:40]

and maybe in the meantime we can figure out something better for this? How does
StructTraits handle nested mojo structs, for example?

+    return;
+  }
+#endif
+  // Avoid loading unnecessary wallpapers in tests without a shell instance.
+  if (ash::Shell::HasInstance()) {
+    ash::Shell::GetInstance()
+        ->desktop_background_controller()
+        ->SetWallpaperImage(image, layout);
+  }
+}
+
 }  // namespace
 
 // This is "wallpaper either scheduled to load, or loading right now".
@@ -202,8 +233,7 @@ class WallpaperManager::PendingWallpaper :
   // There are 4 cases in SetUserWallpaper:
   // 1) gfx::ImageSkia is found in cache.
   //    - Schedule task to (probably) resize it and install:
-  //    call ash::Shell::GetInstance()->desktop_background_controller()->
-  //          SetCustomWallpaper(user_wallpaper, layout);
+  //    call SetWallpaper(user_wallpaper, layout);
   // 2) WallpaperInfo is found in cache
   //    - need to LoadWallpaper(), resize and install.
   // 3) wallpaper path is not NULL, load image URL, then resize, etc...
@@ -257,9 +287,7 @@ class WallpaperManager::PendingWallpaper :
     if (default_) {
       manager->DoSetDefaultWallpaper(account_id_, std::move(on_finish_));
     } else if (!user_wallpaper_.isNull()) {
-      ash::Shell::GetInstance()
-          ->desktop_background_controller()
-          ->SetWallpaperImage(user_wallpaper_, info_.layout);
+      SetWallpaper(user_wallpaper_, info_.layout);
     } else if (!wallpaper_path_.empty()) {
       manager->task_runner_->PostTask(
           FROM_HERE,
@@ -598,11 +626,6 @@ void WallpaperManager::DoSetDefaultWallpaper(
   if (user_manager::UserManager::Get()->IsLoggedInAsKioskApp())
     return;
   wallpaper_cache_.erase(account_id);
-  // Some browser tests do not have a shell instance. As no wallpaper is needed
-  // in these tests anyway, avoid loading one, preventing crashes and speeding
-  // up the tests.
-  if (!ash::Shell::HasInstance())
-    return;
 
   WallpaperResolution resolution = GetAppropriateResolution();
   const bool use_small = (resolution == WALLPAPER_RESOLUTION_SMALL);
@@ -643,8 +666,7 @@ void WallpaperManager::DoSetDefaultWallpaper(
       default_wallpaper_image_->image().height() == 1)
     layout = wallpaper::WALLPAPER_LAYOUT_STRETCH;
 
-  ash::Shell::GetInstance()->desktop_background_controller()->SetWallpaperImage(
-      default_wallpaper_image_->image(), layout);
+  SetWallpaper(default_wallpaper_image_->image(), layout);
 }
 
 void WallpaperManager::SetUserWallpaperInfo(const AccountId& account_id,
@@ -959,11 +981,8 @@ void WallpaperManager::OnWallpaperDecoded(
   // Update the image, but keep the path which was set earlier.
   wallpaper_cache_[account_id].second = user_image->image();
 
-  if (update_wallpaper) {
-    ash::Shell::GetInstance()
-        ->desktop_background_controller()
-        ->SetWallpaperImage(user_image->image(), layout);
-  }
+  if (update_wallpaper)
+    SetWallpaper(user_image->image(), layout);
 }
 
 void WallpaperManager::StartLoad(const AccountId& account_id,
@@ -1068,8 +1087,7 @@ void WallpaperManager::OnDefaultWallpaperDecoded(
     MovableOnDestroyCallbackHolder on_finish,
     std::unique_ptr<user_manager::UserImage> user_image) {
   *result_out = std::move(user_image);
-  ash::Shell::GetInstance()->desktop_background_controller()->SetWallpaperImage(
-      (*result_out)->image(), layout);
+  SetWallpaper((*result_out)->image(), layout);
 }
 
 void WallpaperManager::StartLoadAndSetDefaultWallpaper(