This CL implements functionality to allow an embedder to mark a
debug scope as terminate-on-resume. This results in a termination
exception when that debug scope is left and execution is resumed.
Execution of JavaScript remains possible after a debug scope is
marked as terminate-on-resume (but before execution of the paused
code resumes).
This is used by blink to correctly prevent resuming JavaScript
execution upon reload while being paused at a breakpoint.

This is important for handling reloads while paused at a breakpoint
in blink. The resume command terminates blink's nested message loop
that is used while to keep the frame responsive while the debugger
is paused. But if a reload is triggered while execution is paused
on a breakpoint, but before execution is actually resumed from the
 breakpoint (that means before returning into the V8 JavaScript
frames that are paused on the stack below the C++ frames that belong
to the nested message loop), we re-enter V8 to do tear-down actions
of the old frame. In this case Runtime.terminateExecution() cannot be
used before Debugger.resume(), because the tear-down actions that
re-enter V8 would trigger the termination exception and crash the
browser (because the browser expected the tear-down to succeed).

Hence we introduce this flag on V8 that says: It is OK if someone
re-enters V8 (to execute JS), but upon resuming from the breakpoint
(i.e. returning to the paused frames that are on the stack below),
generate a termination exception.

We deliberated adding a corresponding logic on the blink side (instead
of V8) but we think this is the simplest solution.

More details in the design doc:

https://docs.google.com/document/d/1aO9v0YhoKNqKleqfACGUpwrBUayLFGqktz9ltdgKHMk

Bug: chromium:1004038, chromium:1014415

Change-Id: I896692d4c21cb0acae89c1d783d37ce45b73c113
Reviewed-on: https://chromium-review.googlesource.com/c/v8/v8/+/1924366
Commit-Queue: Sigurd Schneider <sigurds@chromium.org>
Reviewed-by: Toon Verwaest <verwaest@chromium.org>
Reviewed-by: Dmitry Gozman <dgozman@chromium.org>
Reviewed-by: Yang Guo <yangguo@chromium.org>
Cr-Commit-Position: refs/heads/master@{#66084}