Fix PPB_MouseLock.LockMouse crash and add tests.

ppapi/thunk/enter.cc

Index: ppapi/thunk/enter.cc
===================================================================
--- ppapi/thunk/enter.cc	(revision 145683)
+++ ppapi/thunk/enter.cc	(working copy)
@@ -221,9 +221,9 @@
 EnterInstance::EnterInstance(PP_Instance instance,
                              const PP_CompletionCallback& callback)
     : EnterBase(0 /* resource */, callback),
-    // TODO(dmichael): This means that the callback_ we get is not associated
-    //                 even with the instance, but we should handle that for
-    //                 MouseLock (maybe others?).
+      // TODO(dmichael): This means that the callback_ we get is not associated
+      //                 even with the instance, but we should handle that for
+      //                 MouseLock (maybe others?).
       functions_(PpapiGlobals::Get()->GetInstanceAPI(instance)) {
   SetStateForFunctionError(instance, functions_, true);
 }
@@ -237,6 +237,17 @@
   SetStateForFunctionError(instance, functions_, true);
 }
 
+EnterInstanceNoLock::EnterInstanceNoLock(
+    PP_Instance instance,
+    const PP_CompletionCallback& callback)
+    : EnterBase(0 /* resource */, callback),
+      // TODO(dmichael): This means that the callback_ we get is not associated
+      //                 even with the instance, but we should handle that for
+      //                 MouseLock (maybe others?).
+      functions_(PpapiGlobals::Get()->GetInstanceAPI(instance)) {
+  SetStateForFunctionError(instance, functions_, true);
+}
+
 EnterInstanceNoLock::~EnterInstanceNoLock() {
 }