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 a0c95af7b37d3c6d158eac198eb42757dafc5fa0..cc0bd36ab2f2d58147b20c29e47051cd8704e208 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 +54,10 @@ 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 kAlphaEnabledWrongChannel[] =
+    "The alphaEnabled option requires beta channel or newer.";

[benwells, 2014/08/05 23:37:05]

Normally we restrict to dev, not beta. Any reason to let beta use this?

[garykac, 2014/08/07 03:54:00]

I was matching the Shape permissions, but that's not really necessary. Changed
to dev.

+const char kAlphaEnabledMissingPermission[] =
+    "The alphaEnabled option requires app.window.alpha permission.";
 }  // namespace app_window_constants
 
 const char kNoneFrameOption[] = "none";
@@ -234,12 +238,22 @@ bool AppWindowCreateFunction::RunAsync() {
     if (!GetFrameOptions(*options, &create_params))
       return false;
 
-    if (options->transparent_background.get() &&
-        (extension()->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 (!extension()->permissions_data()->HasAPIPermission(
+              APIPermission::kAlphaEnabled)) {
+        error_ = app_window_constants::kAlphaEnabledMissingPermission;
+        return false;
+      }
+#if defined(USE_AURA)
+      create_params.alpha_enabled = *options->alpha_enabled;
+#else
+      // Transparency is only supported on Aura.
+      // Fallback to creating an opaque window (by ignoring alphaEnabled).
+#endif
     }
 
     if (options->hidden.get())