switch ResearchLogger output to json.

use multiple logging files, clean up internal nested class structure.

multi-project commit with I1813b6710ef586d96cf8936662f58b870040d6e5

Bug: 6188932
Change-Id: I438790e28f74747c4c1a48a20c1942a0fd818b6c
diff --git a/java/proguard.flags b/java/proguard.flags
index fd73e12..2b638c6 100644
--- a/java/proguard.flags
+++ b/java/proguard.flags
@@ -37,13 +37,7 @@
 }
 
 -keep class com.android.inputmethod.latin.ResearchLogger {
-  void setLogFileManager(...);
-  void clearAll();
-  com.android.inputmethod.latin.ResearchLogger$LogFileManager getLogFileManager();
-}
-
--keep class com.android.inputmethod.latin.ResearchLogger$LogFileManager {
-  java.lang.String getContents();
+  void flush();
 }
 
 -keep class com.android.inputmethod.keyboard.KeyboardLayoutSet$Builder {