GraphicsLayer::removeAllChildren shouldn't be n^2

This CL changes GraphicsLayer::removeAllChildren to be linear in the number of
children instead of n^2. Previously, we were removing the zero-th element of
the vector in a loop, which causes a shift of all the elements of the vector.
Now we walk the vector from the end, which means remove is constant cost.

This code is called during a compositing update if anything changes about the
GraphicsLayer's children. We didn't actually see this code on our profile
because we're not actually changing the GraphicsLayer tree, but it seemed worth
fixing.

R=ojan@chromium.org

Review URL: https://codereview.chromium.org/187603011

git-svn-id: svn://svn.chromium.org/blink/trunk@168598 bbb929c8-8fbe-4397-9dbb-9b2b20218538
Clean up generate_event_interfaces.py

Follow-up to the split CL.
Just clean-up, no changes to generated EventInterfaces.in.

* Rename to generate_event_interfaces (from "*_names")
This is b/c:
- the output file is called EventInterfaces.in
- the output file is used for both EventFactory and EventNames

* Remove EventInterfaces.in from run-bindings-tests
This file is useless, and adds unnecessary complexity to r-b-t.
The actual output file is trivial:
namespace="Event"

Source/bindings/tests/idls/TestInterfaceEventConstructor
...and I've never looked at it during CG changes.

With it, we need to have 2 passes of compute_interfaces_info,
and a separate temporary file.
Without it, once Terry's CL lands, we'll have no individual files,
and we can just use one temporary directory, removing lots of
temp file complexity.

* Compute source_dir robustly (not using getcwd)

* Refactoring and renaming

Follow-up to:
Split generate_event_interfaces.py from compute_interfaces_info.py
https://codereview.chromium.org/185303008/

BUG=341748
R=haraken

Review URL: https://codereview.chromium.org/186433003

git-svn-id: svn://svn.chromium.org/blink/trunk@168599 bbb929c8-8fbe-4397-9dbb-9b2b20218538