Adding third_party/openh264 build files for encoding

build/gn_migration.gypi

Index: build/gn_migration.gypi
diff --git a/build/gn_migration.gypi b/build/gn_migration.gypi
index 7c8b1a1ff26a6b5ed10929593c22ac0f3a77552e..0943af9c5c83e0e52973037a2628e26407ef85c9 100644
--- a/build/gn_migration.gypi
+++ b/build/gn_migration.gypi
@@ -85,6 +85,7 @@
         '../third_party/WebKit/Source/wtf/wtf_tests.gyp:wtf_unittests',
         '../third_party/leveldatabase/leveldatabase.gyp:env_chromium_unittests',
         '../third_party/libaddressinput/libaddressinput.gyp:libaddressinput_unittests',
+        '../third_party/openh264/testing/openh264_unittests.gyp:openh264_unittests',
         '../third_party/smhasher/smhasher.gyp:pmurhash',
         '../tools/battor_agent/battor_agent.gyp:battor_agent',
         '../tools/telemetry/telemetry.gyp:bitmaptools#host',
@@ -528,8 +529,16 @@
         ['chromecast==1', {
           'dependencies': [
             '../chromecast/chromecast.gyp:cast_shell',
-          ]
-        }]
+          ],
+        }],
+        ['use_openh264==1', {
+          'dependencies': [
+            '../third_party/openh264/openh264.gyp:openh264_common',
+            '../third_party/openh264/openh264.gyp:openh264_processing',
+            '../third_party/openh264/openh264.gyp:openh264_encoder',
+            '../third_party/openh264/openh264.gyp:openh264_decoder',
+          ],
+        }],
       ],
     },
     {