Add support for transparent background API

chrome/browser/extensions/api/app_window/app_window_api.cc

Index: chrome/browser/extensions/api/app_window/app_window_api.cc
diff --git a/chrome/browser/extensions/api/app_window/app_window_api.cc b/chrome/browser/extensions/api/app_window/app_window_api.cc
index 199fbf4b9afcf5c70f65f9c120e15ee1d71df112..4ad6d10e962c96a30bdefa557a1a22389c7186df 100644
--- a/chrome/browser/extensions/api/app_window/app_window_api.cc
+++ b/chrome/browser/extensions/api/app_window/app_window_api.cc
@@ -54,6 +54,15 @@ const char kAlwaysOnTopPermission[] =
     "The \"app.window.alwaysOnTop\" permission is required.";
 const char kInvalidUrlParameter[] =
     "The URL used for window creation must be local for security reasons.";
+
+const char kAlphaEnabledMissingPermission[] =
+    "The alphaEnabled option requires app.window.alpha permission.";
+#if !defined(USE_AURA)

[jackhou1, 2014/07/22 05:35:35]

It might be better to just allow apps to set this regardless of platform, but
add documentation indicating that they need to check AppWindow.alphaEnabled().

[garykac, 2014/07/25 22:50:31]

Done.  Actually, that matches the current doc for this feature.

The downside is that we don't have a way to return a "why" error message
(missing permission vs. platform not supported), but the fallback of creating a
non-opaque window is clearly preferable.

[jackhou1, 2014/07/29 23:39:10]

Oops, I should have been clearer. We should probably still keep the missing
permission error. My reasoning is that a developer would just want to know how
to make the errors go away. So we can tell them to add the permission, but
there's not much they can do about a platform not supporting alpha.

[garykac, 2014/08/04 23:11:53]

Done.

+const char kAlphaEnabledNotSupported[] =
+    "Alpha-blended windows are not supported on this platform.";
+#endif
+const char kAlphaEnabledWrongChannel[] =
+    "The alphaEnabled option requires beta channel or newer.";
 }  // namespace app_window_constants
 
 const char kNoneFrameOption[] = "none";
@@ -232,12 +241,22 @@ bool AppWindowCreateFunction::RunAsync() {
     if (!GetFrameOptions(*options, &create_params))
       return false;
 
-    if (options->transparent_background.get() &&
-        (GetExtension()->permissions_data()->HasAPIPermission(
-             APIPermission::kExperimental) ||
-         CommandLine::ForCurrentProcess()->HasSwitch(
-             switches::kEnableExperimentalExtensionApis))) {
-      create_params.transparent_background = *options->transparent_background;
+    if (options->alpha_enabled.get()) {
+      if (GetCurrentChannel() > chrome::VersionInfo::CHANNEL_BETA) {
+        error_ = app_window_constants::kAlphaEnabledWrongChannel;
+        return false;
+      }
+      if (!GetExtension()->permissions_data()->HasAPIPermission(
+              APIPermission::kAlphaEnabled)) {
+        error_ = app_window_constants::kAlphaEnabledMissingPermission;
+        return false;
+      }
+#if !defined(USE_AURA)
+      error_ = app_window_constants::kAlphaEnabledNotSupported;
+      return false;
+#else
+      create_params.alpha_enabled = *options->alpha_enabled;
+#endif
     }
 
     if (options->hidden.get())