insecure-eventsource-in-main-frame.html is flaky.

BUG=390358
TBR=mkwst@chromium.org

Review URL: https://codereview.chromium.org/367513004

git-svn-id: svn://svn.chromium.org/blink/trunk@177261 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Move ENABLE_MEDIA_CAPTURE to a runtime flag

The effort needs 3 steps:
1. Create the runtime flag interface in blink;
2. Enable the flag for Android from chromium even it does not do anything in blink;
3. Replace compile time guard with runtime flag in blink and remove the build time flag

This is the third step.

BUG=388093

Review URL: https://codereview.chromium.org/358923002

git-svn-id: svn://svn.chromium.org/blink/trunk@177262 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Speculative fix for crash in WebPagePopupImpl::initialize.

ClusterFuzz says there is a null pointer dereference in the function. I suspect
m_widgetClient can be null.

BUG=383150

Review URL: https://codereview.chromium.org/365503006

git-svn-id: svn://svn.chromium.org/blink/trunk@177263 bbb929c8-8fbe-4397-9dbb-9b2b20218538