Force linking as C++ library.

src/core/SkForceCPlusPlusLinking.cpp

+/*
+ * Copyright 2014 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+// This file is intentionally empty.  We add it to the dependencies of skia_lib
+// so that GYP detects that libskia is a C++ library (implicitly depending on
+// the standard library, -lm, etc.) from its file extension.
+//
+// If we didn't do this, GYP would link libskia.so as a C library and we'd get
+// link-time failures for simple binaries that don't themselves depend on the
+// C++ standard library.
+//
+// Even if we try hard not to depend on the standard library, say, never
+// calling new or delete, the compiler can still insert calls on our behalf
+// that make us depend on it anyway: a handler when we call a for a pure
+// virtual, thread-safety guards around statics, probably other similar
+// language constructs.