Preparation work for third_party/openh264 build-from-src CL

This CL reverts the parts of https://codereview.chromium.org/1394983003/ that added dummy unittest binaries for openh264.
This was decided to be a bad move (overhead of binaries, only wanting the tests if flag is set). The unittests will be placed and implemented in content_unittests instead in a follow-up CL.

This CL also pulls in openh264/src source code. The building of this and test code will be added in a follow-up CL.

BUG=500605, 468365

Review URL: https://codereview.chromium.org/1438553002

Cr-Commit-Position: refs/heads/master@{#359548}
diff --git a/DEPS b/DEPS
index 221ef23..2f3b9c3 100644
--- a/DEPS
+++ b/DEPS
@@ -275,6 +275,9 @@
   'src/third_party/catapult':
     Var('chromium_git') + '/external/github.com/catapult-project/catapult.git' + '@' +
     '704c40202baaeb9484af0622aedf41c4a48e0df2',
+
+  'src/third_party/openh264/src':
+    Var('chromium_git') + '/external/github.com/cisco/openh264' + '@' + 'b37cda248234162033e3e11b0335f3131cdfe488',
 }