Add support for retrieving image thumbnails as part of the accessibility tree.

chrome/browser/extensions/api/automation/automation_apitest.cc

Index: chrome/browser/extensions/api/automation/automation_apitest.cc
diff --git a/chrome/browser/extensions/api/automation/automation_apitest.cc b/chrome/browser/extensions/api/automation/automation_apitest.cc
index 8d9d827dad5411794d9e974ed234c3551aca5af3..6c0b9a9bbc9d6014bd003323db191aa55644ff9f 100644
--- a/chrome/browser/extensions/api/automation/automation_apitest.cc
+++ b/chrome/browser/extensions/api/automation/automation_apitest.cc
@@ -145,6 +145,12 @@ IN_PROC_BROWSER_TEST_F(AutomationApiTest, LineStartOffsets) {
       << message_;
 }
 
+IN_PROC_BROWSER_TEST_F(AutomationApiTest, ImageData) {
+  StartEmbeddedTestServer();
+  ASSERT_TRUE(RunExtensionSubtest("automation/tests/tabs", "image_data.html"))
+      << message_;
+}
+
 IN_PROC_BROWSER_TEST_F(AutomationApiTest, TabsAutomationBooleanPermissions) {
   StartEmbeddedTestServer();
   ASSERT_TRUE(RunExtensionSubtest(