aw: Crash on context lost earlier

This CL changes NOTREACHED() to LOG(FATAL) in context lost handling on
RenderThread. WebView currently will intentionally crash in
HardwareRendererViz::OnViz::DisplayOutputSurfaceLost, but it happens on
viz thread later and has no useful information.

Bug: 1112841
Change-Id: I2548c06c32897d586e9d51d143d1dbd2f3fdfc6e
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/2392411Reviewed-by: Bo <boliu@chromium.org>
Commit-Queue: Vasiliy Telezhnikov <vasilyt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#804379}

android_webview/browser/gfx/output_surface_provider_webview.cc

@@ -29,7 +29,12 @@ namespace android_webview {
 namespace {
 
 void OnContextLost(bool synthetic_loss) {
-  NOTREACHED() << "Non owned context lost!";
+  // TODO(https://crbug.com/1112841): Debugging contexts losts. WebView will
+  // intentionally crash in HardwareRendererViz::OnViz::DisplayOutputSurface
+  // that will happen after this callback. That crash happens on viz thread and
+  // doesn't have any useful information. Crash here on RenderThread to
+  // understand the reason of context losts.
+  LOG(FATAL) << "Non owned context lost!";
 }
 
 }  // namespace