Fix Cronet compilation and test errors.

components/cronet/android/java/src/org/chromium/net/ChromiumUrlRequest.java

Index: components/cronet/android/java/src/org/chromium/net/ChromiumUrlRequest.java
diff --git a/components/cronet/android/java/src/org/chromium/net/ChromiumUrlRequest.java b/components/cronet/android/java/src/org/chromium/net/ChromiumUrlRequest.java
index d067cf6559a912cf037252112008ddf399ca80b8..f49bc5f4a8f888410573c96fa4809a22740027a1 100644
--- a/components/cronet/android/java/src/org/chromium/net/ChromiumUrlRequest.java
+++ b/components/cronet/android/java/src/org/chromium/net/ChromiumUrlRequest.java
@@ -397,6 +397,7 @@ public class ChromiumUrlRequest implements HttpUrlRequest {
     }
 
     // All response headers.
+    @SuppressWarnings("unused")

[mmenke, 2014/08/25 19:46:44]

Should this be using the called by native thing?

[mef, 2014/08/25 20:26:18]

Well, it isn't really called by native.

Per discussion with clm@ (correct me if I'm wrong) my understanding of the
problem is:
1. If getAllHeaders is not unused, then proguard removes it.
2. That makes nativeGetAllHeaders also unused, so proguard also removes it.
3. When libcronet.so is loaded it tries to register implementation of
nativeGetAllHeaders, and that fails (CHECKS) as there is no java-side method
declaration (as it is removed in step 2).

I suspect that similar issue may happen if app doesn't have calls to getHeader()
either.

[mef, 2014/08/25 22:12:42]

Per discussion with clm@ this is not a fix, but just a warning suppression.
Real fix is in proguard.cfg (keep class with its native methods).

     public Map<String, List<String>> getAllHeaders() {
         validateHeadersAvailable();
         ResponseHeadersMap result = new ResponseHeadersMap();