[extensions] added checks that function is not empty

[extensions] added checks that function is not empty

ModuleSystem::GetModuleFunction function can return empty v8::Local<v8::Function> if condition in first if inside of this function is false. Then invocation of any methods on this local object will produce a crash, e.g. crbug.com/657561.

BUG=657561
R=rdevlin.cronin@chromium.org

Review-Url: https://codereview.chromium.org/2546853002
Cr-Commit-Position: refs/heads/master@{#435750}
(cherry picked from commit dedd489499fb5b7b47fdd29fef13ffaee2f42dcd)

Committed: https://chromium.googlesource.com/chromium/src/+/3bfdb9a43a060b4c938331d9e397c97a1f0a6c5d

[kozy, 2016-12-03 17:33:38]

Description was changed from

==========
[extensions] added checks that function is not empty

ModuleSystem::GetModuleFunction function can return empty
v8::Local<v8::Function> if condition in first if inside of this function is
false. Then invocation of any methods on this local object will produce a crash,
e.g. crbug.com/657561.

BUG=657561
R=rdevlin.cronin@chromium.org

Review-Url: https://codereview.chromium.org/2546853002
Cr-Commit-Position: refs/heads/master@{#435750}
(cherry picked from commit dedd489499fb5b7b47fdd29fef13ffaee2f42dcd)
==========

to

==========
[extensions] added checks that function is not empty

ModuleSystem::GetModuleFunction function can return empty
v8::Local<v8::Function> if condition in first if inside of this function is
false. Then invocation of any methods on this local object will produce a crash,
e.g. crbug.com/657561.

BUG=657561
R=rdevlin.cronin@chromium.org

Review-Url: https://codereview.chromium.org/2546853002
Cr-Commit-Position: refs/heads/master@{#435750}
(cherry picked from commit dedd489499fb5b7b47fdd29fef13ffaee2f42dcd)

Committed:
https://chromium.googlesource.com/chromium/src/+/3bfdb9a43a060b4c938331d9e397...
==========

[kozy, 2016-12-03 17:33:39]

Committed patchset #1 (id:1) manually as
3bfdb9a43a060b4c938331d9e397c97a1f0a6c5d (tree was closed).