Add support building with OpenMAX DL FFT for WebAudio

BUG=223172

This just adds a gyp variable that enables or disables the use of the OpenMAX DL FFT routines.

Review URL: https://chromiumcodereview.appspot.com/12260023

git-svn-id: http://src.chromium.org/svn/trunk/src/build@190019 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

common.gypi

@@ -660,6 +660,9 @@
       'google_api_key%': '',
       'google_default_client_id%': '',
       'google_default_client_secret%': '',
+
+      # Whether Android uses OpenMAX DL FFT.  Default is no.
+      'use_openmax_dl_fft%': 0,
     },
 
     # Copy conditionally-set variables out one scope.
@@ -918,6 +921,9 @@
     # Set ARM float abi compilation flag.
     'arm_float_abi%': 'softfp',
 
+    # Enable use of OpenMAX DL FFT routines.
+    'use_openmax_dl_fft%': '<(use_openmax_dl_fft)',
+    
     # Enable new NPDevice API.
     'enable_new_npdevice_api%': 0,