Compile in support for the Web Audio API on all platforms. It is still

also controlled by a run-time flag.

For the Chromium build, this will currently compile in a stub (no-op)
implementation of the FFTFrame class.

For Google Chrome branded builds, this will now link against Intel's
MKL on Linux and Windows.

BUG=none
TEST=none
Review URL: http://codereview.chromium.org/6858005

git-svn-id: http://src.chromium.org/svn/trunk/src/build@81818 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

features_override.gypi

@@ -100,7 +100,7 @@
         ],
         'use_threaded_compositing': 1,
       }],
-      ['OS=="mac"', {
+      ['OS=="mac" or OS=="linux" or OS=="win"', {
         'feature_defines': [
           'ENABLE_WEB_AUDIO=1',
         ],