Code cleanup: Simplify redundant code in Inliner.
Code cleanup: Simplify redundant code in Inliner.

Due to ongoing simplifications, the code had two variables that always
referred to the same object (inlineStatements, inlinedBlockStmts) and
reserve_back was called on it twice. The amount of space being reserved
was also wrong, as it accounted for out-param writebacks, which are no
longer supported.

We now only have one name for it, and reserve all the space we need the
first time.

Change-Id: If7b52ff8cef5bc7d4610384b8362f8a6a420f2ac
Reviewed-on: https://skia-review.googlesource.com/c/skia/+/385937
Commit-Queue: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Commit-Queue: Ethan Nicholas <d2cfb8c2f603266f4dc3a6f09acbcc0089603b37@google.com>
Auto-Submit: John Stiles <f4fcf42d3bb5924557f1eeb3be66747535e585da@google.com>
Reviewed-by: Ethan Nicholas <d2cfb8c2f603266f4dc3a6f09acbcc0089603b37@google.com>

google/skia,google/skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,google/skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia,aosp-mirror/platform_external_skia