Add trace events to library loading.

Library loading is costly (especially on low-end devices), but is
absent from traces. This CL fixes that by adding a trace event to
the function that does the loading.

(NOTRY as per advise in crbug.com/736215#c57)
NOTRY=true

Change-Id: I6c7e4d6d39ca91fe5b09105e8e7727718a6f8eab
Reviewed-on: https://chromium-review.googlesource.com/721686
Commit-Queue: Dmitry Skiba <dskiba@chromium.org>
Reviewed-by: agrieve <agrieve@chromium.org>
Reviewed-by: Benoit L <lizeb@chromium.org>
Cr-Commit-Position: refs/heads/master@{#513566}

• base/android/java/src/org/chromium/base/library_loader/LibraryLoader.java[diff]