Add leak checking to all AXPlatformNodeWin unit tests.

Bug: 793123
Change-Id: I2ea589a52a600ae0f0a7e6e2afe00727a6acfacf
Reviewed-on: https://chromium-review.googlesource.com/843240
Commit-Queue: Dominic Mazzoni <dmazzoni@chromium.org>
Reviewed-by: Doug Turner <dougt@chromium.org>
Cr-Commit-Position: refs/heads/master@{#526098}

ui/accessibility/platform/ax_platform_node_win.cc

@@ -367,6 +367,11 @@ AXPlatformNodeWin::~AXPlatformNodeWin() {
     g_unique_id_map.Get().erase(unique_id_);
 }
 
+// static
+size_t AXPlatformNodeWin::GetInstanceCountForTesting() {
+  return g_unique_id_map.Get().size();
+}
+
 const base::char16 AXPlatformNodeWin::kEmbeddedCharacter = L'\xfffc';
 
 void AXPlatformNodeWin::CalculateRelationships() {

ui/accessibility/platform/ax_platform_node_win.h

@@ -292,6 +292,9 @@ class AX_EXPORT __declspec(uuid("26f5641a-246d-457b-a96d-07f3fae6acf2"))
 
   ~AXPlatformNodeWin() override;
 
+  // Return the number of instances of AXPlatformNodeWin, for leak testing.
+  static size_t GetInstanceCountForTesting();
+
   // Represents a non-static text node in IAccessibleHypertext. This character
   // is embedded in the response to IAccessibleText::get_text, indicating the
   // position where a non-static text child object appears.

ui/accessibility/platform/ax_platform_node_win_unittest.cc

@@ -44,6 +44,12 @@ class AXPlatformNodeWinTest : public ui::AXPlatformNodeTest {
     win::CreateATLModuleIfNeeded();
   }
 
+  void TearDown() override {
+    // Destroy the tree and make sure we're not leaking any objects.
+    tree_.reset(nullptr);
+    ASSERT_EQ(0U, AXPlatformNodeWin::GetInstanceCountForTesting());
+  }
+
  protected:
   void BuildRelationships(ComPtr<IAccessible2> accessible) {
     CHECK(accessible);