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

chrome/common/extensions/api/automation.idl

Index: chrome/common/extensions/api/automation.idl
diff --git a/chrome/common/extensions/api/automation.idl b/chrome/common/extensions/api/automation.idl
index 451fc942084478c1c37db561258636b91be49b00..68fd29b3c2263e0963e44a5523c69dbab7c10826 100644
--- a/chrome/common/extensions/api/automation.idl
+++ b/chrome/common/extensions/api/automation.idl
@@ -24,6 +24,7 @@
     documentSelectionChanged,
     expandedChanged,
     focus,
+    imageFrameUpdated,
     hide,
     hover,
     invalidStatusChanged,
@@ -575,6 +576,11 @@
     // Places focus on this node.
     static void focus();
 
+    // Request a data url for the contents of an image, optionally
+    // resized.  Pass zero for maxWidth and/or maxHeight for the
+    // original size.
+    static void getImageData(long maxWidth, long maxHeight);
+
     // Scrolls this node to make it visible.
     static void makeVisible();