This CL was causing inverted rendering in a WebGL application.

This reverts commit 7da98506.

Vectors or matrices that are dynamically indexed as a part of an
l-value generate new statements in the RemoveDynamicIndexing AST
transformation step. SplitSequenceOperator needs to detect this case
and split the sequence operator before statements are generated from
its operands to ensure the correct order of execution.

BUG=angleproject:1341
TEST=angle_end2end_tests

Change-Id: I854f8cce2d46107afa62f48edf3d32c6d5c97eda
Reviewed-on: https://chromium-review.googlesource.com/371643Reviewed-by: Kenneth Russell <kbr@chromium.org>
Commit-Queue: Jamie Madill <jmadill@chromium.org>