Add test_runner API to set the value of an accessibility object.

components/test_runner/web_ax_object_proxy.cc

Index: components/test_runner/web_ax_object_proxy.cc
diff --git a/components/test_runner/web_ax_object_proxy.cc b/components/test_runner/web_ax_object_proxy.cc
index 4ed30f2c44ff2f737e8eacd565882a5ad4a9af0c..27786f9d827dd4241a14ce978fae154ff4bd61d1 100644
--- a/components/test_runner/web_ax_object_proxy.cc
+++ b/components/test_runner/web_ax_object_proxy.cc
@@ -564,6 +564,7 @@ WebAXObjectProxy::GetObjectTemplateBuilder(v8::Isolate* isolate) {
       .SetMethod("decrement", &WebAXObjectProxy::Decrement)
       .SetMethod("showMenu", &WebAXObjectProxy::ShowMenu)
       .SetMethod("press", &WebAXObjectProxy::Press)
+      .SetMethod("setValue", &WebAXObjectProxy::SetValue)
       .SetMethod("isEqual", &WebAXObjectProxy::IsEqual)
       .SetMethod("setNotificationListener",
                  &WebAXObjectProxy::SetNotificationListener)
@@ -1154,6 +1155,15 @@ void WebAXObjectProxy::Press() {
   accessibility_object_.press();
 }
 
+bool WebAXObjectProxy::SetValue(const std::string& value) {
+  accessibility_object_.updateLayoutAndCheckValidity();
+  if (!accessibility_object_.canSetValueAttribute())
+    return false;
+
+  accessibility_object_.setValue(blink::WebString::fromUTF8(value));
+  return true;
+}
+
 bool WebAXObjectProxy::IsEqual(v8::Local<v8::Object> proxy) {
   WebAXObjectProxy* unwrapped_proxy = NULL;
   if (!gin::ConvertFromV8(blink::mainThreadIsolate(), proxy, &unwrapped_proxy))