Speculative fix for SitePerProcessBrowserTest.KeyboardScrollBubblingFromOOPIF

This test was flakily timing out waiting for the scroll to bubble.

It now appears that input events are dropped before the first compositor
commit, so even though the test does not need hit test data to be
available, we wait for it anyway so that we know it's okay to start
sending input events.

Bug: 1014155
Change-Id: I6197fec56e29bf246b210cd4f71d6a84d49694fb
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1863127Reviewed-by: Ken Buchanan <kenrb@chromium.org>
Commit-Queue: Kevin McNee <mcnee@chromium.org>
Cr-Commit-Position: refs/heads/master@{#706187}

content/browser/site_per_process_browsertest.cc

@@ -1823,18 +1823,10 @@ IN_PROC_BROWSER_TEST_F(SitePerProcessBrowserTest, ScrollBubblingFromOOPIFTest) {
   DCHECK_EQ(filter->last_rect().y(), 0);
 }
 
-#if defined(OS_MACOSX) || defined(OS_LINUX)
-// Flaky timeout. https://crbug.com/1014155
-#define MAYBE_KeyboardScrollBubblingFromOOPIF \
-  DISABLED_KeyboardScrollBubblingFromOOPIF
-#else
-#define MAYBE_KeyboardScrollBubblingFromOOPIF KeyboardScrollBubblingFromOOPIF
-#endif
-
 // Tests that scrolling with the keyboard will bubble unused scroll to the
 // OOPIF's parent.
 IN_PROC_BROWSER_TEST_F(SitePerProcessBrowserTest,
-                       MAYBE_KeyboardScrollBubblingFromOOPIF) {
+                       KeyboardScrollBubblingFromOOPIF) {
   GURL main_url(embedded_test_server()->GetURL(
       "a.com", "/frame_tree/page_with_iframe_in_scrollable_div.html"));
   EXPECT_TRUE(NavigateToURL(shell(), main_url));
@@ -1857,6 +1849,11 @@ IN_PROC_BROWSER_TEST_F(SitePerProcessBrowserTest,
   RenderWidgetHostViewBase* rwhv_child = static_cast<RenderWidgetHostViewBase*>(
       iframe_node->current_frame_host()->GetRenderWidgetHost()->GetView());
 
+  // This test does not involve hit testing, but input events could be dropped
+  // by the renderer before the first compositor commit, so we wait here anyway
+  // to avoid that.
+  WaitForHitTestData(iframe_node->current_frame_host());
+
   double initial_y = 0.0;
   ASSERT_TRUE(content::ExecuteScriptAndExtractDouble(
       root,