Turning optimizations on for the bulk of webview

This shaves 85kb from the .dex size and 10kb from memory overhead.

BUG=627139

Review-Url: https://codereview.chromium.org/2240483002
Cr-Commit-Position: refs/heads/master@{#412329}

android_webview/apk/java/proguard.flags

@@ -1,7 +1,10 @@
 # Don't rename anything, it makes stack traces unintelligible. We only allow the
 # obfuscation pass to run so that we can discard attributes like local variable
-# tables.
--keepnames class *** { *; }
+# tables. However, we don't want to lose out on optimizations, so although they
+# can occasionally make the stack trace a bit stranger with inlining, it won't
+# make a big difference for the users seeing the stacktraces. We can always use
+# build/android/stacktrace/java_deobfuscate.py to fix the stacktrace up for us.
+-keepnames,allowoptimization class *** { *; }
 
 # The following chart was created on Aug. 11, 2016, to decide on 3 optimization
 # passes.