DevTools: dispatch mouse events into the main frame when inspector overlay is engaged.

Bug: 944907
Change-Id: I04eac380703adb886cd90751fdd706f9f62107a4
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1534651
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Commit-Queue: Pavel Feldman <pfeldman@chromium.org>
Cr-Commit-Position: refs/heads/master@{#644129}
8 files changed