Test: MHTML document loaded inside a data-URL parent.

In an MHTML document, blink::DocumentLoader::archive_ is transmitted
from parent to children. data-URL aren't loaded from the MHTML archive.
In this case, does it means children of data-URL aren't able to be
loaded from the MHTML archive? Hopefully, it is currently working. They
are able to load from the MHTML document, because |archive_| continue to
be transmitted.

This CL adds a test to ensure this continue to work in the future.

Bug: None.
Change-Id: Icb51dc48691112cf9e45dfe8cb81d389544a0c41
Reviewed-on: https://chromium-review.googlesource.com/c/chromium/src/+/1635669
Commit-Queue: Arthur Sonzogni <arthursonzogni@chromium.org>
Reviewed-by: Kinuko Yasuda <kinuko@chromium.org>
Cr-Commit-Position: refs/heads/master@{#665876}

content/browser/navigation_mhtml_browsertest.cc

@@ -413,4 +413,35 @@ IN_PROC_BROWSER_TEST_F(NavigationMhtmlBrowserTest, IframeContentIdNotFound) {
   EXPECT_FALSE(iframe_navigation.is_error());
 }
 
+// Check MHTML subframe works when its parent is loaded from a data-URL.
+//
+// Frame tree: a1(a2(a3))
+//  -  a1: The main document. Loaded from the MHTML archive.
+//  -  a2: An sub-document loaded from a data-URL.
+//  -  a3: A sub-sub-document loaded from the MHTML archive.
+IN_PROC_BROWSER_TEST_F(NavigationMhtmlBrowserTest, MhtmlIframeInsideDataUrl) {
+  MhtmlArchive mhtml_archive;
+  mhtml_archive.AddHtmlDocument(
+      GURL("http://example.com/a1.html"),
+      "<iframe src=\"data:text/html,"
+      "  <iframe src=&quot;http://example.com/a3.html&quot;></iframe>"
+      "\"></iframe>");
+  mhtml_archive.AddHtmlDocument(GURL("http://example.com/a3.html"),
+                                "<iframe></iframe>");
+  GURL mhtml_url = mhtml_archive.Write("index.mhtml");
+
+  EXPECT_TRUE(NavigateToURL(shell(), mhtml_url));
+
+  RenderFrameHostImpl* a1_rfh = main_frame_host();
+  ASSERT_EQ(1u, a1_rfh->child_count());
+  RenderFrameHostImpl* a2_rfh = a1_rfh->child_at(0)->current_frame_host();
+  ASSERT_EQ(1u, a2_rfh->child_count());
+
+  // Check a3 is properly loaded. EvalJs("document.body.innerHTML") can't be
+  // used, because javascript is disabled. Instead, check it was able to load an
+  // iframe.
+  RenderFrameHostImpl* a3_rfh = a2_rfh->child_at(0)->current_frame_host();
+  ASSERT_EQ(1u, a3_rfh->child_count());
+}
+
 }  // namespace content