Expose RTT and throughput estimates from Cronet

components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java

Index: components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
diff --git a/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java b/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
index 819347d57a1cad185362e7e0315d0afc3d09fe71..66a07f83f2f33dcdb7158ee20476291a46a53b8f 100644
--- a/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
+++ b/components/cronet/android/java/src/org/chromium/net/impl/CronetUrlRequestContext.java
@@ -24,6 +24,7 @@ import org.chromium.net.EffectiveConnectionType;
 import org.chromium.net.NetworkQualityRttListener;
 import org.chromium.net.NetworkQualityThroughputListener;
 import org.chromium.net.RequestFinishedInfo;
+import org.chromium.net.RttThroughputValues;
 import org.chromium.net.UrlRequest;
 import org.chromium.net.urlconnection.CronetHttpURLConnection;
 import org.chromium.net.urlconnection.CronetURLStreamHandlerFactory;
@@ -94,6 +95,27 @@ public class CronetUrlRequestContext extends CronetEngine {
     @GuardedBy("mNetworkQualityLock")
     private int mEffectiveConnectionType = EffectiveConnectionType.TYPE_UNKNOWN;
 
+    /**
+     * Current estimate of the HTTP RTT (in milliseconds) computed by the
+     * network quality estimator.
+     */
+    @GuardedBy("mNetworkQualityLock")
+    private int mHttpRttMs = RttThroughputValues.INVALID_RTT_THROUGHPUT_VALUE;
+
+    /**
+     * Current estimate of the transport RTT (in milliseconds) computed by the
+     * network quality estimator.
+     */
+    @GuardedBy("mNetworkQualityLock")
+    private int mTransportRttMs = RttThroughputValues.INVALID_RTT_THROUGHPUT_VALUE;
+
+    /**
+     * Current estimate of the downstream throughput (in kilobits per second)
+     * computed by the network quality estimator.
+     */
+    @GuardedBy("mNetworkQualityLock")
+    private int mDownstreamThroughputKbps = RttThroughputValues.INVALID_RTT_THROUGHPUT_VALUE;
+
     @GuardedBy("mNetworkQualityLock")
     private final ObserverList<NetworkQualityRttListener> mRttListenerList =
             new ObserverList<NetworkQualityRttListener>();
@@ -334,6 +356,45 @@ public class CronetUrlRequestContext extends CronetEngine {
         }
     }
 
+    @Override
+    public int getHttpRttMsec() {
+        if (!mNetworkQualityEstimatorEnabled) {
+            throw new IllegalStateException("Network quality estimator must be enabled");
+        }
+        synchronized (mNetworkQualityLock) {
+            synchronized (mLock) {

[RyanSturm, 2016/10/14 21:21:32]

I'm not happy with the locking order pattern in this file. Could 

synchronized (mLock) {
 checkHaveAdapter();
}

happen before

synchronized (mNetworkQualityLock)

instead of inside it?

[tbansal1, 2016/10/14 21:50:29]

This pattern was introduced in
https://codereview.chromium.org/2283243002/diff/120001/components/cronet/andr....
Not sure why it is this way.

[RyanSturm, 2016/10/14 22:19:12]

Any chance you want to try to fix it in this CL? There doesn't seem to be a need
to have nested locks, and I would hate to block the IO thread if mLock is stuck
doing something.

[tbansal1, 2016/10/14 22:44:43]

If we do want to fix it, I would prefer to do it in a separate CL.
I am not sure how separating the two locks makes it faster. If mLock is stuck,
then
even if the locks are separated, NQE functions still have to wait.

[RyanSturm, 2016/10/14 22:55:38]

If getEffectiveConnectionTypeChanged gets blocked on mLock on the UI thread,
then calling onEffectiveConnectionTypeChanged will block the IO thread, but if
mNetworkQualityLock weren't held then onEffectiveConnectionTypeChanged could
just set it and leave.

Change it in another CL. Doesn't seem high priority.

[tbansal1, 2016/10/14 23:31:49]

Yeah, I need to check with clm@ why it was done this way.

+                checkHaveAdapter();
+            }
+            return mHttpRttMs;
+        }
+    }
+
+    @Override
+    public int getTransportRttMsec() {
+        if (!mNetworkQualityEstimatorEnabled) {
+            throw new IllegalStateException("Network quality estimator must be enabled");
+        }
+        synchronized (mNetworkQualityLock) {
+            synchronized (mLock) {
+                checkHaveAdapter();
+            }
+            return mTransportRttMs;
+        }
+    }
+
+    @Override
+    public int getDownstreamThroughputKbps() {
+        if (!mNetworkQualityEstimatorEnabled) {
+            throw new IllegalStateException("Network quality estimator must be enabled");
+        }
+        synchronized (mNetworkQualityLock) {
+            synchronized (mLock) {
+                checkHaveAdapter();
+            }
+            return mDownstreamThroughputKbps;
+        }
+    }
+
     @VisibleForTesting
     @Override
     public void configureNetworkQualityEstimatorForTesting(
@@ -527,6 +588,17 @@ public class CronetUrlRequestContext extends CronetEngine {
 
     @SuppressWarnings("unused")
     @CalledByNative
+    private void onRTTOrThroughputEstimatesComputed(
+            final int httpRttMs, final int transportRttMs, final int downstreamThroughputKbps) {
+        synchronized (mNetworkQualityLock) {
+            mHttpRttMs = httpRttMs;
+            mTransportRttMs = transportRttMs;
+            mDownstreamThroughputKbps = downstreamThroughputKbps;
+        }
+    }
+
+    @SuppressWarnings("unused")
+    @CalledByNative
     private void onRttObservation(final int rttMs, final long whenMs, final int source) {
         synchronized (mNetworkQualityLock) {
             for (final NetworkQualityRttListener listener : mRttListenerList) {