Revert of Use BoringSSL in the implementation of ClearKey for Chromecast....

Revert of Use BoringSSL in the implementation of ClearKey for Chromecast. (patchset #1 id:1 of https://codereview.chromium.org/1130893008/)

Reason for revert:
Temporary revert until Monday (blocked on some other internal changes).

Original issue's description:
> Use BoringSSL in the implementation of ClearKey for Chromecast.
> (Previously, this was used only with the "Chrome" branding).
>
> BUG= 488572
>
> R=gunsch@chromium.org
>
> Committed: https://crrev.com/defd2af08f3753687cb2d86b34bbec9da31ccbab
> Cr-Commit-Position: refs/heads/master@{#330156}

TBR=ddorwin@chromium.org,dougsteed@chromium.org
NOPRESUBMIT=true
NOTREECHECKS=true
NOTRY=true
BUG= 488572

Review URL: https://codereview.chromium.org/1141243003

Cr-Commit-Position: refs/heads/master@{#330230}

chromecast/media/media.gyp

@@ -195,7 +195,17 @@
         '../../base/base.gyp:base',
         '../../crypto/crypto.gyp:crypto',
         '../../media/media.gyp:media',
-        '../../third_party/boringssl/boringssl.gyp:boringssl',
+      ],
+      'conditions': [
+        ['chromecast_branding=="Chrome"', {
+          'dependencies': [
+            '../internal/cast_system.gyp:openssl',
+          ],
+        }, {
+          'dependencies': [
+            '../../third_party/boringssl/boringssl.gyp:boringssl',
+          ],
+        }],
       ],
       'sources': [
         'cma/pipeline/audio_pipeline.cc',