accessibility: Fix CFI bad cast errors.

Running content_unittests on Android with CFI bad cast checks enabled
[1] revealed two bad cast errors in accessibility: a bad cast
from CountedBrowserAccessibility to BrowserAccessibilityAndroid
in browser_accessibility_manager_android.cc:69 and from
TestBrowserAccessibilityManager to BrowserAccessibilityManagerAndroid
in browser_accessibility_android.cc:148.

In the former case, the code from BrowserAccessibilityAndroid can
easily be inlined into the caller, so this patch does that. In the
latter case, the caller is accessing a field that is only present
on BrowserAccessibilityManagerAndroid, so the fix is to derive
TestBrowserAccessibilityManager from BrowserAccessibilityManagerAndroid
on Android platforms.

This change hopefully fixes the memory error that was detected by
asan. In a followup I plan to attempt to re-enable these tests on
Android with asan.

[1] https://build.chromium.org/p/chromium.clang/builders/ToTAndroidCFI/builds/397/steps/content_unittests%20on%20Android

Bug: 469376
Change-Id: I4560451ec276ab1057feac3ef906daf5fc045ca3
Reviewed-on: https://chromium-review.googlesource.com/780884
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Dominic Mazzoni <dmazzoni@chromium.org>
Cr-Commit-Position: refs/heads/master@{#518352}

content/browser/accessibility/browser_accessibility_manager_android.cc

@@ -8,6 +8,7 @@
 #include "content/browser/accessibility/browser_accessibility_android.h"
 #include "content/browser/accessibility/web_contents_accessibility_android.h"
 #include "content/common/accessibility_messages.h"
+#include "ui/accessibility/ax_role_properties.h"
 
 namespace content {
 
@@ -65,9 +66,7 @@ bool BrowserAccessibilityManagerAndroid::ShouldExposePasswordText() {
 
 BrowserAccessibility* BrowserAccessibilityManagerAndroid::GetFocus() {
   BrowserAccessibility* focus = BrowserAccessibilityManager::GetFocus();
-  BrowserAccessibilityAndroid* android_focus =
-      static_cast<BrowserAccessibilityAndroid*>(focus);
-  if (!android_focus->IsEditableText())
+  if (!ui::IsEditField(focus->GetRole()))
     return GetActiveDescendant(focus);
   return focus;
 }

content/browser/accessibility/one_shot_accessibility_tree_search_unittest.cc

@@ -10,12 +10,23 @@
 #include "base/test/scoped_task_environment.h"
 #include "content/browser/accessibility/browser_accessibility.h"
 #include "content/browser/accessibility/browser_accessibility_manager.h"
+#ifdef OS_ANDROID
+#include "content/browser/accessibility/browser_accessibility_manager_android.h"
+#endif
 #include "testing/gtest/include/gtest/gtest.h"
 
 namespace content {
 
 namespace {
 
+#ifdef OS_ANDROID
+class TestBrowserAccessibilityManager
+    : public BrowserAccessibilityManagerAndroid {
+ public:
+  TestBrowserAccessibilityManager(const ui::AXTreeUpdate& initial_tree)
+      : BrowserAccessibilityManagerAndroid(initial_tree, nullptr, nullptr) {}
+};
+#else
 class TestBrowserAccessibilityManager : public BrowserAccessibilityManager {
  public:
   TestBrowserAccessibilityManager(
@@ -24,6 +35,7 @@ class TestBrowserAccessibilityManager : public BrowserAccessibilityManager {
                                     nullptr,
                                     new BrowserAccessibilityFactory()) {}
 };
+#endif
 
 }  // namespace