Fix flaky NQE cronet test

components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java

Index: components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
diff --git a/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java b/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
index 0426d28ee178f1c8e6477e167597e555eb16d542..7fcce83272686cc09ba01df6c41526aa0a1f768e 100644
--- a/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
+++ b/components/cronet/android/test/javatests/src/org/chromium/net/CronetUrlRequestContextTest.java
@@ -282,12 +282,18 @@ public class CronetUrlRequestContextTest extends CronetTestBase {
                 true, true, testExecutor);
         mTestFramework.mCronetEngine.addRttListener(networkQualityListener);
         mTestFramework.mCronetEngine.addThroughputListener(networkQualityListener);
-        TestUrlRequestCallback callback = new TestUrlRequestCallback();
-        UrlRequest urlRequest =
-                mTestFramework.mCronetEngine.createRequest(mUrl, callback, callback.getExecutor());
-        urlRequest.start();
-        callback.blockForDone();
-        testExecutor.runAllTasks();
+
+        // Throughput observation is posted to network quality estimator, and running two requests

[xunjieli, 2016/05/24 01:54:43]

The comment is a little vague, and I don't quite understand why starting a
second request forces the NQE throughput callback to be flushed.
When will we know the throughput observation of the first request ? Will it
definitely occur before the second request?

[tbansal1, 2016/05/24 16:57:08]

I updated the comment. Let me know if it is still confusing. 

+        // ensures that the observation corresponding to the first request is posted in time.
+        for (int i = 0; i < 2; ++i) {
+            TestUrlRequestCallback callback = new TestUrlRequestCallback();
+            UrlRequest urlRequest = mTestFramework.mCronetEngine.createRequest(
+                    mUrl, callback, callback.getExecutor());
+            urlRequest.start();
+            callback.blockForDone();
+            testExecutor.runAllTasks();
+        }
+
         assertTrue(networkQualityListener.rttObservationCount() > 0);
         assertTrue(networkQualityListener.throughputObservationCount() > 0);
         mTestFramework.mCronetEngine.shutdown();