Adding build_opus as a switch in GYP.

This is to allow not building Opus. On non-chromium non-gyp chases, one can let WebRTC depend on other Opus builds.

BUG=
R=kjellander@webrtc.org, tina.legrand@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/43739004

Cr-Commit-Position: refs/heads/master@{#8754}
git-svn-id: http://webrtc.googlecode.com/svn/trunk@8754 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/build/common.gypi

@@ -91,6 +91,7 @@
     'build_vp9%': 1,
     'build_ssl%': 1,
     'build_openmax_dl%': 1,
+    'build_opus%': 1,
 
     # Disable by default
     'have_dbus_glib%': 0,

webrtc/build/webrtc.gni

@@ -43,6 +43,7 @@ declare_args() {
   rtc_build_libvpx = true
   rtc_build_vp9 = true
   rtc_build_ssl = true
+  rtc_build_opus = true
 
   # Disable by default.
   rtc_have_dbus_glib = false

webrtc/modules/audio_coding/BUILD.gn

@@ -666,14 +666,14 @@ source_set("webrtc_opus") {
 
   deps = [ ":audio_encoder_interface" ]
 
-  if (build_with_mozilla) {
-    include_dirs = [ getenv("DIST") + "/include/opus" ]
-  } else {
+  if (rtc_build_opus) {
     configs += [ "../..:common_config" ]
     public_configs = [ "../..:common_inherited_config" ]
 
     deps += [ rtc_opus_dir ]
     forward_dependent_configs_from = [ rtc_opus_dir ]
+  } else if (build_with_mozilla) {
+    include_dirs = [ getenv("DIST") + "/include/opus" ]
   }
 }
 

webrtc/modules/audio_coding/codecs/opus/opus.gypi

@@ -12,12 +12,7 @@
       'target_name': 'webrtc_opus',
       'type': 'static_library',
       'conditions': [
-        ['build_with_mozilla==1', {
-          # Mozilla provides its own build of the opus library.
-          'include_dirs': [
-            '$(DIST)/include/opus',
-           ]
-        }, {
+        ['build_opus==1', {
           'dependencies': [
             '<(opus_dir)/opus.gyp:opus'
           ],
@@ -30,6 +25,15 @@
               '<(opus_dir)/src/celt',
             ],
           },
+        }, {
+          'conditions': [
+            ['build_with_mozilla==1', {
+              # Mozilla provides its own build of the opus library.
+              'include_dirs': [
+                '$(DIST)/include/opus',
+              ]
+            }],
+          ],
         }],
       ],
       'dependencies': [