Add variable use_concatenated_impulse_responses to control whether webaudio uses concatenated impul…

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 277b5b32e6005d8e4234979796881d443e0a5907..fa829b3b79c39e99d2ae16fc346aba09baeff34f 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -652,6 +652,10 @@
         }],
       ],
 
+      # Set this to 1 to enable use of concatenated impulse responses
+      # for the HRTF panner in WebAudio.
+      'use_concatenated_impulse_responses': 0,
+
       # Set this to 1 to use the Google-internal file containing
       # official API keys for Google Chrome even in a developer build.
       # Setting this variable explicitly to 1 will cause your build to
@@ -1500,6 +1504,9 @@
       ['enable_google_now==1', {
         'grit_defines': ['-D', 'enable_google_now'],
       }],
+      ['use_concatenated_impulse_responses==1', {
+        'grit_defines': ['-D', 'use_concatenated_impulse_responses'],
+      }],
       ['clang_use_chrome_plugins==1 and OS!="win"', {
         'clang_chrome_plugins_flags': [
           '<!@(<(DEPTH)/tools/clang/scripts/plugin_flags.sh)'