Add WebstoreInlineInstaller (downloads store data, shows the install UI, and starts the install).

chrome/common/extensions/extension_constants.cc

Index: chrome/common/extensions/extension_constants.cc
diff --git a/chrome/common/extensions/extension_constants.cc b/chrome/common/extensions/extension_constants.cc
index 19b9632768cdbb35bbc5d9903c14afaba105dbef..96289ea4ccf400c23805f208ef541b6c85829b08 100644
--- a/chrome/common/extensions/extension_constants.cc
+++ b/chrome/common/extensions/extension_constants.cc
@@ -425,6 +425,10 @@ std::string GetWebstoreItemDetailURLPrefix() {
   return GetWebstoreLaunchURL() + "/detail/";
 }
 
+GURL GetWebstoreItemJsonDataURL(const std::string& extension_id) {
+  return GURL(GetWebstoreItemDetailURLPrefix() + extension_id + "?output=json");
+}
+
 const char* kGalleryUpdateHttpUrl =
     "http://clients2.google.com/service/update2/crx";
 const char* kGalleryUpdateHttpsUrl =