BitBlt returns a BOOL value, which should be taken care in ScreenCapturerWinGdi.
Meanwhile, this change also replaces assert() / abort() with RTC_DCHECK() /
RTC_CHECK() / RTC_NOTREACHED().
This change cannot fix the bug, the reason of the issue is still unknown, but it
is still the right thing to do.
In ScreenCapturerIntegrationTest, each frame will be captured at most 600 times.
Since the test case fails, which means the ScreenCapturerWinGdi consistently
returns a white frame for 600 times under a certain state. With this change,
instead of returning white frame, ScreenCapturerWinGdi will return a temporary
error. But I do not think a ScreenCapturerWinGdi can automatically recover by
retrying.
BUG=webrtc:6843
Review-Url: https://codereview.webrtc.org/2553353002
Cr-Commit-Position: refs/heads/master@{#15465}
2cd872a939