[Webapps] Add switch to about:flags

Adds a flag to about:flags to make the "Add to Homescreen"
menu item visible.  Requires a downstream patch to actually put
the menu item in.

BUG=286156

Review URL: https://chromiumcodereview.appspot.com/23676005

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@221770 0039d316-1c4b-4281-b951-d872f2087c98

chrome/app/generated_resources.grd

@@ -5473,6 +5473,12 @@ Keep your key file in a safe place. You will need it to create new versions of y
           Enable the accessibility tab switcher for Android.
         </message>
       </if>
+      <message name="IDS_FLAGS_ENABLE_ADD_TO_HOMESCREEN_NAME" desc="Name of the flag to enable the add to homescreen menu item.">
+        Enable Add to Homescreen
+      </message>
+      <message name="IDS_FLAGS_ENABLE_ADD_TO_HOMESCREEN_DESCRIPTION" desc="Description of the flag to enable the add to homescreen menu item.">
+        Enable the add to homescreen menu item.
+      </message>
       <message name="IDS_TOUCH_EVENTS_NAME" desc="Title of the touch-events flag." >
         Enable touch events
       </message>

chrome/browser/about_flags.cc

@@ -1636,6 +1636,17 @@ const Experiment kExperiments[] = {
     kOsDesktop,
     SINGLE_VALUE_TYPE(switches::kEnableDeviceMotion)
   },
+  {
+    "enable-add-to-homescreen",
+    IDS_FLAGS_ENABLE_ADD_TO_HOMESCREEN_NAME,
+    IDS_FLAGS_ENABLE_ADD_TO_HOMESCREEN_DESCRIPTION,
+    kOsAndroid,
+#if defined(OS_ANDROID)
+    SINGLE_VALUE_TYPE(switches::kEnableAddToHomescreen)
+#else
+    SINGLE_VALUE_TYPE("")
+#endif
+  },
 };
 
 const Experiment* experiments = kExperiments;

chrome/common/chrome_switches.cc

@@ -1493,6 +1493,9 @@ const char kFakeCloudPolicyType[]           = "fake-cloud-policy-type";
 const char kEnableAccessibilityTabSwitcher[] =
     "enable-accessibility-tab-switcher";
 
+// Makes the "Add to Homescreen" shortcut visible.
+const char kEnableAddToHomescreen[]         = "enable-add-to-homescreen";
+
 // Enables the new NTP.
 const char kEnableNewNTP[]                  = "enable-new-ntp";
 

chrome/common/chrome_switches.h

@@ -407,6 +407,7 @@ extern const char kFakeCloudPolicyType[];
 
 #if defined(OS_ANDROID)
 extern const char kEnableAccessibilityTabSwitcher[];
+extern const char kEnableAddToHomescreen[];
 extern const char kEnableNewNTP[];
 extern const char kEnableTranslate[];
 extern const char kTabletUI[];