Ensure zero suggest can handle XSSI-escaped output.

chrome/browser/autocomplete/zero_suggest_provider.cc

Index: chrome/browser/autocomplete/zero_suggest_provider.cc
diff --git a/chrome/browser/autocomplete/zero_suggest_provider.cc b/chrome/browser/autocomplete/zero_suggest_provider.cc
index 07d7c2c6ebacfcd7e34db58544981648fd5c9732..089e4256751eb46d21e16230bbf1e7c525162e10 100644
--- a/chrome/browser/autocomplete/zero_suggest_provider.cc
+++ b/chrome/browser/autocomplete/zero_suggest_provider.cc
@@ -133,11 +133,24 @@ void ZeroSuggestProvider::OnURLFetchComplete(const net::URLFetcher* source) {
       source->GetStatus().is_success() && source->GetResponseCode() == 200;
 
   if (request_succeeded) {
-    JSONStringValueSerializer deserializer(json_data);
-    deserializer.set_allow_trailing_comma(true);
-    scoped_ptr<Value> data(deserializer.Deserialize(NULL, NULL));
-    if (data.get())
-      ParseSuggestResults(*data.get());
+    // The JSON response should be an array.
+    for (size_t response_start_index = json_data.find("["), i = 0;

[H Fung, 2013/11/30 00:46:27]

I'm not sure why we try up to 5 times and why we ignore contiguous open
brackets, but I guess this works.  I'm not sure if it might be better to put
this code in a separate function in SearchProvider to avoid duplicate code?

+         response_start_index != std::string::npos && i < 5;
+         response_start_index = json_data.find("[", 1), i++) {
+      // Remove any XSSI guards to allow for JSON parsing.
+      if (response_start_index > 0)
+        json_data.erase(0, response_start_index);
+
+      JSONStringValueSerializer deserializer(json_data);
+      deserializer.set_allow_trailing_comma(true);
+      int error_code = 0;
+      scoped_ptr<Value> data(deserializer.Deserialize(&error_code, NULL));
+      if (error_code == 0) {
+        if (data.get())
+          ParseSuggestResults(*data.get());
+        break;
+      }
+    }
   }
   done_ = true;