Fix include of isolate.gypi

Recent changes in GYP seem to have broken our previous
"hack" for getting the GYP rule for .isolate files
imported from the Chromium build/isolate.gypi.

The best solution for now is to remove the hack
and check in a copy of Chromium's src/build/isolate.gypi
in WebRTC's build/ dir instead. A similar approach is
used for our build/protoc.gypi file.

TEST=On Linux, I successfully ran:
gclient runhooks
ninja -C out/Release
and verified a bunch of .isolated files were created in
out/Release (which didn't happen before this patch).

I also renamed the build/isolate.gypi from Chromium to
ensure that our own is used and not that one (in case any
paths would be incorrect).

I also ran build/gyp_chromium in a Chromium checkout
with WebRTC in third_party/webrtc having this patch applied
to ensure GYP processing was still working.

Finally, I verified that the same project generation and
compilation from a Chromium checkout worked the way we build
our Android native tests, using:
. build/android/envsetup.sh
GYP_DEFINES="$GYP_DEFINES include_tests=1 enable_tracing=1" gclient runhooks
ninja -C out/Release android_builder_webrtc

BUG=1916
R=andrew@webrtc.org

Review URL: https://webrtc-codereview.appspot.com/2338004

git-svn-id: http://webrtc.googlecode.com/svn/trunk@4907 4adac7df-926f-26a2-2b94-8c16560cd09d

webrtc/modules/audio_coding/neteq/neteq.gypi

@@ -251,10 +251,10 @@
               'target_name': 'neteq_unittests_run',
               'type': 'none',
               'dependencies': [
-                '<(import_isolate_path):import_isolate_gypi',
                 'neteq_unittests',
               ],
               'includes': [
+                '../../../build/isolate.gypi',
                 'neteq_unittests.isolate',
               ],
               'sources': [

webrtc/modules/audio_coding/neteq4/neteq.gypi

@@ -200,10 +200,10 @@
               'target_name': 'audio_decoder_unittests_run',
               'type': 'none',
               'dependencies': [
-                '<(import_isolate_path):import_isolate_gypi',
                 'audio_decoder_unittests',
               ],
               'includes': [
+                '../../../build/isolate.gypi',
                 'audio_decoder_unittests.isolate',
               ],
               'sources': [