Use ScopedTaskEnvironment instead of MessageLoop in RenderViewTest.

components/printing/test/print_web_view_helper_browsertest.cc

Index: components/printing/test/print_web_view_helper_browsertest.cc
diff --git a/components/printing/test/print_web_view_helper_browsertest.cc b/components/printing/test/print_web_view_helper_browsertest.cc
index add6995883e3adafbf34b5d197d3a60d533144ba..0cd8115925d9340af1099f7d11340df55b785ff0 100644
--- a/components/printing/test/print_web_view_helper_browsertest.cc
+++ b/components/printing/test/print_web_view_helper_browsertest.cc
@@ -172,7 +172,7 @@ class PrintWebViewHelperTestBase : public content::RenderViewTest {
 
   void PrintWithJavaScript() {
     ExecuteJavaScriptForTests("window.print();");
-    ProcessPendingMessages();
+    base::RunLoop().RunUntilIdle();
   }
 
   // The renderer should be done calculating the number of rendered pages
@@ -242,7 +242,7 @@ class PrintWebViewHelperTestBase : public content::RenderViewTest {
 #if BUILDFLAG(ENABLE_BASIC_PRINTING)
   void OnPrintPages() {
     GetPrintWebViewHelper()->OnPrintPages();
-    ProcessPendingMessages();
+    base::RunLoop().RunUntilIdle();
   }
 #endif  // BUILDFLAG(ENABLE_BASIC_PRINTING)
 
@@ -270,7 +270,7 @@ class PrintWebViewHelperTestBase : public content::RenderViewTest {
 #if BUILDFLAG(ENABLE_BASIC_PRINTING)
   void OnPrintForPrintPreview(const base::DictionaryValue& dict) {
     GetPrintWebViewHelper()->OnPrintForPrintPreview(dict);
-    ProcessPendingMessages();
+    base::RunLoop().RunUntilIdle();
   }
 #endif  // BUILDFLAG(ENABLE_BASIC_PRINTING)
 
@@ -365,7 +365,7 @@ TEST_F(MAYBE_PrintWebViewHelperTest, AllowUserOriginatedPrinting) {
   SendWebMouseEvent(mouse_event);
   mouse_event.SetType(blink::WebInputEvent::kMouseUp);
   SendWebMouseEvent(mouse_event);
-  ProcessPendingMessages();
+  base::RunLoop().RunUntilIdle();
 
   VerifyPageCount(1);
   VerifyPagesPrinted(true);