Remove redundant field initialization in Java code.

Leaving fields uninitialized results in fewer compiled bytes than
initializing fields to default values. This CL shrinks the uncompressed
size of classes.dex by 8.6 kb for proguarded chrome_public_apk.

Change was made with Android Studio (Analyze > Run inspection by name >
Redundant field initialization), and fixes all instances in projects
currently generated by build/android/gradle/generate_gradle.py.

NOPRESUBMIT=true

BUG=670001

Review-Url: https://codereview.chromium.org/2548013002
Cr-Commit-Position: refs/heads/master@{#438216}
186 files changed