Moving flags out of base_proguard_config make it usable by other .apks

android_webview/apk/java/proguard.flags

 # 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 *** { *; }
 
+# The following chart was created on Aug. 11, 2016, to decide on 3 optimization
+# passes.
+# optimization passes | time | .dex size |      dirty memory
+# -----------------------------------------------------------------
+#          1          | 0:13 |  1022588  |         97772
+#          2          | 0:17 |  1019200  |         97472
+#          3          | 0:18 |  1018472  |         97424
+#          4          | 0:21 |  1018392  |         97416
+#          5          | 0:26 |  1018360  |         97416
+-optimizationpasses 3
+
+# Class merging messes up stacktraces beyond the point of them being
+# deobfuscatable. If turned on, it would give us a 1% reduction in .dex size.
+-optimizations !class/merging/*
+
+# Allowing Proguard to change modifiers. This change shrinks the .dex size by
+# 3.7%.
+-allowaccessmodification
 
 # Keep the factory and its public members; it's the main entry point used by the
 # framework.
 -keep class com.android.webview.chromium.WebViewChromiumFactoryProvider {
     public *;
 }
 
 # This is the main entry point for APIs. It is kept to make developing with
 # unreleased Android easier.
 -keep class com.android.webview.chromium.WebViewChromium {
@@ skipping 40 matching lines @@
 #TODO(hush): remove after N release. crbug.com/546762
 -keep class com.android.webview.chromium.ContentSettingsAdapter {
   public void setDisabledActionModeMenuItems(int);
   public int getDisabledActionModeMenuItems();
 }
 
 # Ignore notes and warnings about the support library, which uses reflection and
 # may reference classes no longer in the SDK.
 -dontnote android.support.**
 -dontwarn android.support.**