[AW NS] Fix failing ClientOnReceivedError2Test tests: header is not necessarily empty.

Update the relevant failing ClientOnReceivedError2Test tests
(listed below) to not check for empty headers. Request headers
in onReceivedError callback may or may not be empty, this is
an implementation detail. In the network service code path
they may e.g. contain user agent, see https://crbug.com/893573.

Also add a comment in tests explaining this.

Fixed tests:
-ClientOnReceivedError2Test.testIframeSubresource
-ClientOnReceivedError2Test.testImageSubresource
-ClientOnReceivedError2Test.testMainFrame
-ClientOnReceivedError2Test.testUserGesture
-ClientOnReceivedError2Test.testUserGestureForIframeSubresource

BUG=893573,841556

Cq-Include-Trybots: master.tryserver.chromium.android:android_mojo
Change-Id: Ic6322c7d9720b62709c2b506639108ed2a36a188
Reviewed-on: https://chromium-review.googlesource.com/c/1356801Reviewed-by: Tobias Sargeant <tobiasjs@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Commit-Queue: Tim Volodine <timvolodine@chromium.org>
Cr-Commit-Position: refs/heads/master@{#612777}

android_webview/javatests/src/org/chromium/android_webview/test/ClientOnReceivedError2Test.java

@@ -115,8 +115,8 @@ public class ClientOnReceivedError2Test {
         Assert.assertEquals(BAD_HTML_URL, request.url);
         Assert.assertEquals("GET", request.method);
         Assert.assertNotNull(request.requestHeaders);
-        // No actual request has been made, as the host name can't be resolved.
-        Assert.assertTrue(request.requestHeaders.isEmpty());
+        // request headers may or may not be empty, this is an implementation detail,
+        // in the network service code path they may e.g. contain user agent, crbug.com/893573.
         Assert.assertTrue(request.isMainFrame);
         Assert.assertFalse(request.hasUserGesture);
         AwWebResourceError error = onReceivedError2Helper.getError();
@@ -149,8 +149,8 @@ public class ClientOnReceivedError2Test {
         Assert.assertEquals(BAD_HTML_URL, request.url);
         Assert.assertEquals("GET", request.method);
         Assert.assertNotNull(request.requestHeaders);
-        // No actual request has been made, as the host name can't be resolved.
-        Assert.assertTrue(request.requestHeaders.isEmpty());
+        // request headers may or may not be empty, this is an implementation detail,
+        // in the network service code path they may e.g. contain user agent, crbug.com/893573.
         Assert.assertTrue(request.isMainFrame);
         Assert.assertTrue(request.hasUserGesture);
         AwWebResourceError error = onReceivedError2Helper.getError();
@@ -176,8 +176,8 @@ public class ClientOnReceivedError2Test {
         Assert.assertEquals(BAD_HTML_URL, request.url);
         Assert.assertEquals("GET", request.method);
         Assert.assertNotNull(request.requestHeaders);
-        // No actual request has been made, as the host name can't be resolved.
-        Assert.assertTrue(request.requestHeaders.isEmpty());
+        // request headers may or may not be empty, this is an implementation detail,
+        // in the network service code path they may e.g. contain user agent, crbug.com/893573.
         Assert.assertFalse(request.isMainFrame);
         Assert.assertFalse(request.hasUserGesture);
         AwWebResourceError error = onReceivedError2Helper.getError();
@@ -214,8 +214,8 @@ public class ClientOnReceivedError2Test {
         Assert.assertEquals(BAD_HTML_URL, request.url);
         Assert.assertEquals("GET", request.method);
         Assert.assertNotNull(request.requestHeaders);
-        // No actual request has been made, as the host name can't be resolved.
-        Assert.assertTrue(request.requestHeaders.isEmpty());
+        // request headers may or may not be empty, this is an implementation detail,
+        // in the network service code path they may e.g. contain user agent, crbug.com/893573.
         Assert.assertFalse(request.isMainFrame);
         Assert.assertTrue(request.hasUserGesture);
         AwWebResourceError error = onReceivedError2Helper.getError();
@@ -242,8 +242,8 @@ public class ClientOnReceivedError2Test {
         Assert.assertEquals(imageUrl, request.url);
         Assert.assertEquals("GET", request.method);
         Assert.assertNotNull(request.requestHeaders);
-        // No actual request has been made, as the host name can't be resolved.
-        Assert.assertTrue(request.requestHeaders.isEmpty());
+        // request headers may or may not be empty, this is an implementation detail,
+        // in the network service code path they may e.g. contain user agent, crbug.com/893573.
         Assert.assertFalse(request.isMainFrame);
         Assert.assertFalse(request.hasUserGesture);
         AwWebResourceError error = onReceivedError2Helper.getError();

testing/buildbot/filters/mojo.fyi.network_webview_instrumentation_test_apk.filter

@@ -92,13 +92,6 @@
 -org.chromium.android_webview.test.ClientOnPageStartedTest.testNotCalledForDownloadPdf
 -org.chromium.android_webview.test.ClientOnPageStartedTest.testRendererInitiatedRedirectHangingNavigation
 
-# https://crbug.com/893573
--org.chromium.android_webview.test.ClientOnReceivedError2Test.testIframeSubresource
--org.chromium.android_webview.test.ClientOnReceivedError2Test.testImageSubresource
--org.chromium.android_webview.test.ClientOnReceivedError2Test.testMainFrame
--org.chromium.android_webview.test.ClientOnReceivedError2Test.testUserGesture
--org.chromium.android_webview.test.ClientOnReceivedError2Test.testUserGestureForIframeSubresource
-
 # https://crbug.com/893575
 -org.chromium.android_webview.test.CookieManagerStartupTest.testShouldInterceptRequestDeadlock
 -org.chromium.android_webview.test.CookieManagerStartupTest.testStartup