Allow speech input feature to be disabled.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 512c8e9d3f10677d7fc363b77b9f663e27ce5603..258165604866fd230e79010b3b0532c7bb3a7849 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -197,6 +197,9 @@
       # Safe browsing is compiled in by default. Set to 0 to disable.
       'safe_browsing%': 1,
 
+      # Speech input is compiled in by default. Set to 0 to disable.
+      'input_speech%': 1,
+
       # If this is set, the clang plugins used on the buildbot will be used.
       # Run tools/clang/scripts/update.sh to make sure they are compiled.
       # This causes 'clang_chrome_plugins_flags' to be set.
@@ -385,6 +388,7 @@
     'p2p_apis%': '<(p2p_apis)',
     'configuration_policy%': '<(configuration_policy)',
     'safe_browsing%': '<(safe_browsing)',
+    'input_speech%': '<(input_speech)',
     'clang_use_chrome_plugins%': '<(clang_use_chrome_plugins)',
     'asan%': '<(asan)',
     'enable_register_protocol_handler%': '<(enable_register_protocol_handler)',
@@ -652,6 +656,7 @@
         'proprietary_codecs%': '<(proprietary_codecs)',
         'safe_browsing%': 0,
         'configuration_policy%': 0,
+        'input_speech%': 0,
 
         # Builds the gtest targets as a shared_library.
         # TODO(michaelbai): Use the fixed value 'shared_library' once it
@@ -1005,6 +1010,9 @@
       ['configuration_policy==1', {
         'defines': ['ENABLE_CONFIGURATION_POLICY'],
       }],
+      ['input_speech==1', {
+        'defines': ['ENABLE_INPUT_SPEECH'],
+      }],
       ['fastbuild!=0', {
 
         'conditions': [