Fix unbounded allocation of GL queries

Check to see if previously-allocated queries are done before allocating
new ones. It turns out that destroying a massive list of queries
accounts for 50% of our watchdog timeouts in the GPU process.

BUG=398072

Review URL: https://codereview.chromium.org/642993002

Cr-Commit-Position: refs/heads/master@{#299164}

cc/resources/texture_uploader.cc

@@ -116,6 +116,12 @@ double TextureUploader::EstimatedTexturesPerSecond() {
 }
 
 void TextureUploader::BeginQuery() {
+  // Check to see if any of the pending queries are free before allocating a
+  // new one. If this is not done, queries may be allocated without bound.
+  // http://crbug.com/398072
+  if (available_queries_.empty())
+    ProcessQueries();
+
   if (available_queries_.empty())
     available_queries_.push_back(Query::Create(gl_));