GN: Implement voice engine, common audio, audio coding and audio processing

NOTICE: Assembly offsets generation for audio processing will
not be ported to GN and the process of removing them is tracked
in https://code.google.com/p/webrtc/issues/detail?id=3580.

The GN files are based upon the GYP files as of r7009.

BUG=3441
TESTED=Passing builds with:
gn gen out/Default --args="build_with_chromium=false" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false is_debug=true" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false aec_debug_dump=true" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false aec_untrusted_delay_for_testing=true" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false prefer_fixed_point=true" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false os=\"android\" cpu_arch=\"arm\" is_clang=false" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false os=\"android\" cpu_arch=\"arm\" arm_version=7 is_clang=false" && ninja -C out/Default

I don't know how to setup the mips toolchain to test the following, but it's out of scope for the GN effort for now:
gn gen out/Default --args="build_with_chromium=false cpu_arch=\"mipsel\" mips_dsp_rev=0" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false cpu_arch=\"mipsel\" mips_dsp_rev=1" && ninja -C out/Default
gn gen out/Default --args="build_with_chromium=false cpu_arch=\"mipsel\" mips_dsp_rev=2" && ninja -C out/Default

Compilation of Chromium's 'all' target with src/third_party/webrtc
symlinked to the WebRTC checkout with this CL applied, both
with the default GN settings and using
--args="is_debug=false os=\"android\" cpu_arch=\"arm\""

R=andrew@webrtc.org, brettw@chromium.org

Review URL: https://webrtc-codereview.appspot.com/15999004

git-svn-id: http://webrtc.googlecode.com/svn/trunk/webrtc@7012 4adac7df-926f-26a2-2b94-8c16560cd09d

1 files changed, 15 insertions, 3 deletions

diff --git a/build/webrtc.gni b/build/webrtc.gni
index 5b3fe183..cae81664 100644
--- a/build/webrtc.gni
+++ b/build/webrtc.gni
@@ -6,20 +6,22 @@
 # in the file PATENTS.  All contributing project authors may
 # be found in the AUTHORS file in the root of the source tree.
 
+import("//build/config/arm.gni")
+
 declare_args() {
   # Assume Chromium build for now, since that's the priority case for getting GN
   # up and running with WebRTC.
   build_with_chromium = true
   build_with_libjingle = true
 
+  # Disable this to avoid building the Opus audio codec.
+  include_opus = true
+
   # Adds video support to dependencies shared by voice and video engine.
   # This should normally be enabled; the intended use is to disable only
   # when building voice engine exclusively.
   enable_video = true
 
-  # Disable this to not build libvpx and instead use an externally provided lib.
-  build_libvpx = true
-
   # Selects fixed-point code where possible.
   prefer_fixed_point = false
 
@@ -51,6 +53,11 @@ declare_args() {
 
   enable_android_opensl = true
 
+  # Link-Time Optimizations.
+  # Executes code generation at link-time instead of compile-time.
+  # https://gcc.gnu.org/wiki/LinkTimeOptimization
+  use_lto = false
+
   if (build_with_chromium) {
     # Exclude pulse audio on Chromium since its prerequisites don't require
     # pulse audio.
@@ -94,4 +101,9 @@ declare_args() {
   if (cpu_arch == "arm") {
     prefer_fixed_point = true
   }
+
+  # WebRTC builds ARM v7 Neon instruction set optimized code for both iOS and
+  # Android, which is why we currently cannot use the variables in
+  # //build/config/arm.gni (since it disables Neon for Android).
+  build_armv7_neon = (cpu_arch == "arm" && arm_version == 7)
 }