Minor cleanup in GrTessellatingPathRenderer.

Minor cleanup in GrTessellatingPathRenderer.

Vertex counts are always exact, so don't bother handling the case
where they're different. Just assert.
Rename variables to reflect.

BUG=skia:

Committed: https://skia.googlesource.com/skia/+/9389b871c3b0f06bb34626cf9bdbfe0c93779327

[Stephen White, 2015-08-31 19:13:05]

senorblanco@chromium.org changed reviewers:
+ bsalomon@google.com

[Stephen White, 2015-08-31 19:13:17]

senorblanco@chromium.org changed reviewers:
+ senorblanco@chromium.org

[Stephen White, 2015-08-31 19:13:17]

Brian: PTAL. Thanks!

[Stephen White, 2015-08-31 19:13:26]

The CQ bit was checked by senorblanco@chromium.org to run a CQ dry run

[commit-bot: I haz the power, 2015-08-31 19:13:34]

Dry run: CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1322023002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1322023002/1

[commit-bot: I haz the power, 2015-08-31 19:19:06]

The CQ bit was unchecked by commit-bot@chromium.org

[commit-bot: I haz the power, 2015-08-31 19:19:06]

Dry run: This issue passed the CQ dry run.

[bsalomon, 2015-08-31 19:41:16]

On 2015/08/31 19:19:06, commit-bot: I haz the power wrote:
> Dry run: This issue passed the CQ dry run.

lgtm

[Stephen White, 2015-08-31 19:41:38]

The CQ bit was checked by senorblanco@chromium.org

[commit-bot: I haz the power, 2015-08-31 19:41:48]

CQ is trying da patch. Follow status at
 https://chromium-cq-status.appspot.com/patch-status/1322023002/1
View timeline at
 https://chromium-cq-status.appspot.com/patch-timeline/1322023002/1

[commit-bot: I haz the power, 2015-08-31 19:42:26]

Committed patchset #1 (id:1) as
https://skia.googlesource.com/skia/+/9389b871c3b0f06bb34626cf9bdbfe0c93779327

[Stephen White, 2015-09-02 15:50:41]

A revert of this CL (patchset #1 id:1) has been created in
https://codereview.chromium.org/1321723006/ by senorblanco@chromium.org.

The reason for reverting is: Patch is incorrect -- floating point errors can
cause zero-area monotone polys to be skipped, resulting in a smaller vertex
count than estimated.

Reproduce as follows: 

out/Debug/SampleApp --slide Fuzzer --msaa 4

switch to GPU mode. Result:

../../src/gpu/batches/GrTessellatingPathRenderer.cpp:1500: failed assertion
"static_cast<int>(end - verts) == vertexCount".