Introduce CSSAssertSetFailFunc and CSSAsserFail to throw managed exception

Summary:
- Define CSS_ASSERT_FAIL_ENABLED for P/Invoke (Visual Studio project already has it)
- Pass managed delegate pointer to unmanaged side via P/Invoke.
- CSSAssertFail will call the managed delegate when assert failed.
- The delegate will throw managed exception.

Reviewed By: emilsjolander

Differential Revision: D3982084

fbshipit-source-id: 058a87c10ca89238362be4d8759cc00dd0c9b376

CSSLayout/CSSLayout.h

@@ -122,6 +122,10 @@ typedef CSSSize (*CSSMeasureFunc)(void *context,
                                   CSSMeasureMode heightMode);
 typedef void (*CSSPrintFunc)(void *context);
 
+#ifdef CSS_ASSERT_FAIL_ENABLED
+typedef void (*CSSAssertFailFunc)(const char *message);
+#endif
+
 // CSSNode
 WIN_EXPORT CSSNodeRef CSSNodeNew();
 WIN_EXPORT void CSSNodeInit(const CSSNodeRef node);
@@ -206,4 +210,10 @@ CSS_NODE_LAYOUT_PROPERTY(float, Width);
 CSS_NODE_LAYOUT_PROPERTY(float, Height);
 CSS_NODE_LAYOUT_PROPERTY(CSSDirection, Direction);
 
+#ifdef CSS_ASSERT_FAIL_ENABLED
+// Assert
+WIN_EXPORT void CSSAssertSetFailFunc(CSSAssertFailFunc func);
+WIN_EXPORT void CSSAssertFail(const char *message);
+#endif
+
 CSS_EXTERN_C_END