[AW NS] provide proper user_agent in onDownloadStart callback and add tests

The user agent is not necessarily set in the request headers
during InterceptDownload (e.g. because they are not initialized yet).

In this patch:
- make sure a user agent is set in the case of uninitialized headers.
- make sure the user agent override is used when it is set by using
WebSetting.setUserAgentString().
- add download related instrumentation tests for the user agent
setting.

Tests:
- AwContentsTest.testDownload
- AwContentsTest.testDownloaWithCustomUserAgent

BUG=893568,841556

Cq-Include-Trybots: master.tryserver.chromium.android:android_mojo
Change-Id: Ifc432fd93dd68ffb7416a25b6d6d1b5d1021e327
Reviewed-on: https://chromium-review.googlesource.com/c/1477606
Commit-Queue: Tim Volodine <timvolodine@chromium.org>
Reviewed-by: Richard Coles <torne@chromium.org>
Cr-Commit-Position: refs/heads/master@{#634890}

android_webview/browser/aw_download_manager_delegate.cc

@@ -4,14 +4,15 @@
 
 #include "android_webview/browser/aw_download_manager_delegate.h"
 
+#include "android_webview/browser/aw_content_browser_client.h"
+#include "android_webview/browser/aw_contents_client_bridge.h"
 #include "base/files/file_path.h"
+#include "base/task/post_task.h"
 #include "components/download/public/common/download_danger_type.h"
 #include "components/download/public/common/download_item.h"
-
-#include "android_webview/browser/aw_contents_client_bridge.h"
-#include "base/task/post_task.h"
 #include "content/public/browser/browser_task_traits.h"
 #include "content/public/browser/browser_thread.h"
+#include "content/public/browser/web_contents.h"
 
 namespace android_webview {
 
@@ -70,10 +71,16 @@ bool AwDownloadManagerDelegate::InterceptDownloadIfApplicable(
     const std::string& request_origin,
     int64_t content_length,
     content::WebContents* web_contents) {
+  std::string aw_user_agent = web_contents->GetUserAgentOverride();
+  if (aw_user_agent.empty()) {
+    // use default user agent if nothing is provided
+    aw_user_agent = user_agent.empty() ? GetUserAgent() : user_agent;
+  }
   base::PostTaskWithTraits(
       FROM_HERE, {content::BrowserThread::UI},
-      base::BindOnce(&DownloadStartingOnUIThread, web_contents, url, user_agent,
-                     content_disposition, mime_type, content_length));
+      base::BindOnce(&DownloadStartingOnUIThread, web_contents, url,
+                     aw_user_agent, content_disposition, mime_type,
+                     content_length));
   return true;
 }
 

android_webview/browser/aw_download_manager_delegate.h

@@ -10,6 +10,12 @@
 #include "base/supports_user_data.h"
 #include "content/public/browser/download_manager_delegate.h"
 
+namespace content {
+
+class WebContents;
+
+}  // namespace content
+
 namespace android_webview {
 
 // Android WebView does not use Chromium downloads, so implement methods here to

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

@@ -343,10 +343,26 @@ public class AwContentsTest {
     @Feature({"AndroidWebView", "Downloads"})
     @SmallTest
     public void testDownload() throws Throwable {
+        downloadAndCheck(null);
+    }
+
+    @Test
+    @Feature({"AndroidWebView", "Downloads"})
+    @SmallTest
+    public void testDownloadWithCustomUserAgent() throws Throwable {
+        downloadAndCheck("Custom User Agent");
+    }
+
+    private void downloadAndCheck(String customUserAgent) throws Throwable {
         AwTestContainerView testView =
                 mActivityTestRule.createAwTestContainerViewOnMainSync(mContentsClient);
         AwContents awContents = testView.getAwContents();
 
+        if (customUserAgent != null) {
+            AwSettings awSettings = mActivityTestRule.getAwSettingsOnUiThread(awContents);
+            awSettings.setUserAgentString(customUserAgent);
+        }
+
         final String data = "download data";
         final String contentDisposition = "attachment;filename=\"download.txt\"";
         final String mimeType = "text/plain";
@@ -370,6 +386,13 @@ public class AwContentsTest {
             Assert.assertEquals(contentDisposition, downloadStartHelper.getContentDisposition());
             Assert.assertEquals(mimeType, downloadStartHelper.getMimeType());
             Assert.assertEquals(data.length(), downloadStartHelper.getContentLength());
+            Assert.assertFalse(downloadStartHelper.getUserAgent().isEmpty());
+            if (customUserAgent != null) {
+                Assert.assertEquals(customUserAgent, downloadStartHelper.getUserAgent());
+            } else {
+                Assert.assertEquals(
+                        downloadStartHelper.getUserAgent(), AwSettings.getDefaultUserAgent());
+            }
         } finally {
             webServer.shutdown();
         }