Fixed memory leak in InterfacePtrSet::RemovePtr

Bug: 840949
Change-Id: Ied53a2d1cccb0a0c474d8b9cfb76bad1a8d83987
Reviewed-on: https://chromium-review.googlesource.com/1050581
Commit-Queue: Daniel Murphy <dmurph@chromium.org>
Reviewed-by: John Abd-El-Malek <jam@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557618}

mojo/public/cpp/bindings/interface_ptr_set.h

@@ -77,8 +77,10 @@ class PtrSet {
     if (it == ptrs_.end())
       return Ptr<Interface>();
     Ptr<Interface> ptr;
-    if (it->second)
+    if (it->second) {
       ptr = it->second->Take();
+      delete it->second.get();
+    }
     ptrs_.erase(it);
     return ptr;
   }