Minor fixes to wording in NDK perf documentation.
Minor fixes to wording in NDK perf documentation.

Tested:
Built the docs, verified they look ok in HTML.

Change-Id: I63fe420b44d92234f6310e471c19c2332b68bcc7

google/fplutil,google/fplutil,google/fplutil,google/fplutil,google/fplutil,google/fplutil