Add Create() function to AudioCodecBridge and VideoCodecBridge to allow return of null pointers

If codec is not supported, we should allow null pointers to be returned when trying to create a MediaCodecBridge.

BUG=233420

Review URL: https://chromiumcodereview.appspot.com/14932020

git-svn-id: http://src.chromium.org/svn/trunk/src/build@202323 4ff67af0-8c30-449e-8e8b-ad334ec8d88c

all_android.gyp

@@ -100,6 +100,7 @@
             '../components/components.gyp:components_unittests_apk',
             '../content/content.gyp:content_browsertests_apk',
             '../content/content.gyp:content_unittests_apk',
+            '../content/content.gyp:video_decode_accelerator_unittest_apk',
             '../gpu/gpu.gyp:gl_tests_apk',
             '../gpu/gpu.gyp:gpu_unittests_apk',
             '../ipc/ipc.gyp:ipc_tests_apk',