Allow direct executors in cronet.

components/cronet/android/api/src/org/chromium/net/UrlRequest.java

Index: components/cronet/android/api/src/org/chromium/net/UrlRequest.java
diff --git a/components/cronet/android/api/src/org/chromium/net/UrlRequest.java b/components/cronet/android/api/src/org/chromium/net/UrlRequest.java
index 932300014c8ae71380fe11d6772e0e5a6f3eef1b..01bcfc8aeff3391e9fab1c6e33eb20867012e4e8 100644
--- a/components/cronet/android/api/src/org/chromium/net/UrlRequest.java
+++ b/components/cronet/android/api/src/org/chromium/net/UrlRequest.java
@@ -56,6 +56,7 @@ public interface UrlRequest {
         UploadDataProvider mUploadDataProvider;
         // Executor to call upload data provider back on.
         Executor mUploadDataProviderExecutor;
+        private boolean mAllowDirectExecutor = false;
 
         /**
          * Creates a builder for {@link UrlRequest} objects. All callbacks for
@@ -227,6 +228,21 @@ public interface UrlRequest {
         }
 
         /**
+         * Marks that the executors this request will use to notify callbacks (for
+         * {@code UploadDataProvider}s and {@code UrlRequest.Callback}s) is intentionally performing
+         * inline execution, like Guava's directExecutor or
+         * {@link java.util.concurrent.ThreadPoolExecutor.CallerRunsPolicy}.
+         *
+         * <p><b>Warning:</b> This option makes it easy to accidentally block the network thread.
+         * It should not be used if your callbacks perform disk I/O, acquire locks, or call into
+         * other code you don't carefully control and audit.
+         */
+        public Builder allowDirectExecutor() {
+            mAllowDirectExecutor = true;
+            return this;
+        }
+
+        /**
          * Associates the annotation object with this request. May add more than one.
          * Passed through to a {@link RequestFinishedInfo.Listener},
          * see {@link RequestFinishedInfo#getAnnotations}.
@@ -258,7 +274,8 @@ public interface UrlRequest {
          */
         public UrlRequest build() {
             final UrlRequest request = mCronetEngine.createRequest(mUrl, mCallback, mExecutor,
-                    mPriority, mRequestAnnotations, mDisableCache, mDisableConnectionMigration);
+                    mPriority, mRequestAnnotations, mDisableCache, mDisableConnectionMigration,
+                    mAllowDirectExecutor);
             if (mMethod != null) {
                 request.setHttpMethod(mMethod);
             }
@@ -266,7 +283,12 @@ public interface UrlRequest {
                 request.addHeader(header.first, header.second);
             }
             if (mUploadDataProvider != null) {
-                request.setUploadDataProvider(mUploadDataProvider, mUploadDataProviderExecutor);
+                if (mAllowDirectExecutor) {
+                    request.setUploadDataProvider(mUploadDataProvider, mUploadDataProviderExecutor);
+                } else {
+                    request.setUploadDataProvider(mUploadDataProvider,
+                            new DirectPreventingExecutor(mUploadDataProviderExecutor));
+                }
             }
             return request;
         }