Check that a valid RawVarData has been created before calling a funct…

…ion on it

Currently the PP_Var type that is deserialized from an incoming IPC
is invalid, RawVarData::Create will return a nullptr which we will
try to call a function on. Instead we should just fail to deserialize
the entire message in that case.

BUG=693007

Review-Url: https://codereview.chromium.org/2705933002
Cr-Commit-Position: refs/heads/master@{#451541}

ppapi/proxy/raw_var_data.cc

@@ -198,6 +198,8 @@ std::unique_ptr<RawVarDataGraph> RawVarDataGraph::Read(
       return nullptr;
     PP_VarType var_type = static_cast<PP_VarType>(type);
     result->data_.push_back(base::WrapUnique(RawVarData::Create(var_type)));
+    if (!result->data_.back())
+      return nullptr;
     if (!result->data_.back()->Read(var_type, m, iter))
       return nullptr;
   }