Enable DumpAccessibilityTree tests to use cross-process iframes.

content/browser/accessibility/dump_accessibility_browsertest_base.h

Index: content/browser/accessibility/dump_accessibility_browsertest_base.h
diff --git a/content/browser/accessibility/dump_accessibility_browsertest_base.h b/content/browser/accessibility/dump_accessibility_browsertest_base.h
index 21ae32a1faf94fa21fa3c867aa56f6bf085e1d2f..7430ff5b046662f3955fd75a0566a63f06431ad9 100644
--- a/content/browser/accessibility/dump_accessibility_browsertest_base.h
+++ b/content/browser/accessibility/dump_accessibility_browsertest_base.h
@@ -9,6 +9,7 @@
 #include "base/strings/string16.h"
 #include "build/build_config.h"
 #include "content/browser/accessibility/accessibility_tree_formatter.h"
+#include "content/browser/site_per_process_browsertest.h"
 #include "content/public/test/content_browser_test.h"
 
 namespace content {
@@ -19,7 +20,7 @@ namespace content {
 //
 // The system was inspired by WebKit/Blink LayoutTests, but customized for
 // testing accessibility in Chromium.
-class DumpAccessibilityTestBase : public ContentBrowserTest {
+class DumpAccessibilityTestBase : public SitePerProcessBrowserTest {

[nasko, 2016/01/07 00:07:37]

nit: It seems that this tests uses only the setup of the test class. It might be
easier to just copy those over.

[dmazzoni, 2016/01/07 19:19:08]

Done.

  public:
   DumpAccessibilityTestBase();
   ~DumpAccessibilityTestBase() override;
@@ -79,11 +80,12 @@ class DumpAccessibilityTestBase : public ContentBrowserTest {
   // until the given string (e.g., "text") appears in the resulting dump.
   // A test can make some changes to the document, then append a magic string
   // indicating that the test is done, and this framework will wait for that
-  // string to appear before comparing the results.
+  // string to appear before comparing the results. There can be multiple
+  // @WAIT-FOR: directives.
   void ParseHtmlForExtraDirectives(
       const std::string& test_html,
       std::vector<AccessibilityTreeFormatter::Filter>* filters,
-      std::string* wait_for);
+      std::vector<std::string>* wait_for);
 
   // Create the right AccessibilityTreeFormatter subclass.
   AccessibilityTreeFormatter* CreateAccessibilityTreeFormatter();