Add platform_app flag to manifest.

chrome/browser/about_flags.cc

Index: chrome/browser/about_flags.cc
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index 0feb4811ac4e1e025d8a65d7c062c1d901cb1dcc..3f587d85160d4573f87da1e05e4a7462fd00181f 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -443,6 +443,13 @@ const Experiment kExperiments[] = {
     kOsAll,
     SINGLE_VALUE_TYPE(switches::kEnableMediaSource)
   },
+  {

[Aaron Boodman, 2011/11/04 05:45:16]

Keep in mind that once you put something in about:flags, users will start
clicking it and filing bugs. This happened to Tessa's recent work on lazy
background pages.

It seems like this isn't to the level yet where that would be useful, so I
recommend skipping about:flags for now, and just having the command-line flag.

+    "platform-apps",
+    IDS_FLAGS_ENABLE_PLATFORM_APPS_NAME,
+    IDS_FLAGS_ENABLE_PLATFORM_APPS_DESCRIPTION,
+    kOsAll,
+    SINGLE_VALUE_TYPE(switches::kEnablePlatformApps)
+  },
 };
 
 const Experiment* experiments = kExperiments;