XFA: merge patch from CL 733693003, get rid of FX_LPCSTR cast

Get rid of FX_LPCSTR cast.

Follow up on https://codereview.chromium.org/733693003

R=brucedawson@chromium.org, tsepez@chromium.org

Review URL: https://codereview.chromium.org/809993004
diff --git a/fpdfsdk/src/fsdk_baseannot.cpp b/fpdfsdk/src/fsdk_baseannot.cpp
index 90e22d3..9b669e9 100644
--- a/fpdfsdk/src/fsdk_baseannot.cpp
+++ b/fpdfsdk/src/fsdk_baseannot.cpp
@@ -1058,7 +1058,7 @@
 		pStreamDict->SetAtRect("BBox", rcBBox);		
 	}
 	
-	pStream->SetData((FX_BYTE*)(FX_LPCSTR)sContents, sContents.GetLength(), FALSE, FALSE);
+	pStream->SetData((FX_BYTE*)sContents.c_str(), sContents.GetLength(), FALSE, FALSE);
 }
 
 #define BA_ANNOT_MINWIDTH			1