Add a [rtc_]build_with_neon variable to unify conditions.

webrtc/build/common.gypi

Index: webrtc/build/common.gypi
diff --git a/webrtc/build/common.gypi b/webrtc/build/common.gypi
index 26b0de367a806f56f050ad386a50711e77c51b20..e93034fbebeabd25184db44a01c6de8d4073b2dd 100644
--- a/webrtc/build/common.gypi
+++ b/webrtc/build/common.gypi
@@ -121,6 +121,10 @@
     # enable schannel on windows.
     'use_legacy_ssl_defaults%': 0,
 
+    # Determines whether NEON code will be built. It might not be selected at

[kjellander_webrtc, 2015/06/18 09:06:23]

I assume you mean "WebRTC doesn't support selecting it at runtime" ? Please
phrase it that way since it's unclear to me in the current comment.

[Andrew MacDonald, 2015/06/25 01:09:09]

No, that's not what I meant :)

Just removed the run-time note to avoid confusion.

+    # run-time.
+    'build_with_neon%': 0,
+
     'conditions': [
       ['build_with_chromium==1', {
         # Exclude pulse audio on Chromium since its prerequisites don't require
@@ -152,6 +156,9 @@
       ['target_arch=="arm" or target_arch=="arm64"', {
         'prefer_fixed_point%': 1,
       }],
+      ['(target_arch=="arm" and (arm_neon==1 or arm_neon_optional==1)) or target_arch=="arm64"', {
+        'build_with_neon%': 1,

[Andrew MacDonald, 2015/06/17 22:46:21]

gyp wasn't picking up the variable changes in the other scopes, so let's just do
it at one place here. Matches gn better anyway.

+      }],
       ['OS!="ios" and (target_arch!="arm" or arm_version>=7) and target_arch!="mips64el"', {
         'rtc_use_openmax_dl%': 1,
       }, {