Main motivation for this is to save binary size. The change causes linker dead
code elimination to exclude the blockfile backend on Android (at least until
somebody references the wrong symbol). This change saves 68KiB for me on a
release official build on Android.

Removes the about:flags entry on Android to avoid confusing the users. The
command-line flag stays and makes the backend initialization fail: that's what
you asked for.

Makes CACHE_BACKEND_DEFAULT behave exactly as CACHE_BACKEND_SIMPLE on Android.
This simplifies testing: clients like shader cache should be using the default
backend and should not care about the differences. Yay for more simplecache
testing! The Simple Backend supports all necessary features to make it the
default. PNACL cache is currently not tested on Android, not supporting it in
the histogram collection code now.

BUG=342890
[email protected]

Review URL: https://codereview.chromium.org/207503006

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@259957 0039d316-1c4b-4281-b951-d872f2087c98
diff --git a/chrome/browser/about_flags.cc b/chrome/browser/about_flags.cc
index ce5ef11..095ca8f 100644
--- a/chrome/browser/about_flags.cc
+++ b/chrome/browser/about_flags.cc
@@ -1357,7 +1357,7 @@
     "enable-simple-cache-backend",
     IDS_FLAGS_ENABLE_SIMPLE_CACHE_BACKEND_NAME,
     IDS_FLAGS_ENABLE_SIMPLE_CACHE_BACKEND_DESCRIPTION,
-    kOsAll,
+    kOsWin | kOsMac | kOsLinux | kOsCrOS,
     MULTI_VALUE_TYPE(kSimpleCacheBackendChoices)
   },
   {