Set enable_hangouts_services_extension in build/common.gypi.

build/common.gypi

Index: build/common.gypi
diff --git a/build/common.gypi b/build/common.gypi
index 5e37d9d4d88bb556a7aee01cf1fe4310a5dbdd60..60d09b7fb501092e32b622d332f35d38ff1d6aa2 100644
--- a/build/common.gypi
+++ b/build/common.gypi
@@ -2394,6 +2394,12 @@
       ['cfi_vptr==1 or cfi_derived_cast==1 or cfi_unrelated_cast==1', {
         'use_lto%': 1,
       }],
+      # Enable the Hangouts services extension for official builds.

[kjellander_chromium, 2015/05/20 15:47:03]

The comment doesn't really add anything that cannot be already be read from the
code. Skip it?

[pbos, 2015/05/20 17:23:54]

Done.

+      ['branding=="Chrome" and buildtype=="Official"', {
+        'enable_hangout_services_extension%': 1,
+      }, {
+        'enable_hangout_services_extension%': 0,
+      }],
     ],
 
     # The path to the ANGLE library.