pathops: Add missing header guards in two files.

Guards were missing in SkIntersectionHelper.h and
SkPathOpsTSect.h.

BUG=skia:
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1914873002

Review URL: https://codereview.chromium.org/1914873002

src/pathops/SkIntersectionHelper.h

@@ -4,6 +4,9 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
+#ifndef SkIntersectionHelper_DEFINED
+#define SkIntersectionHelper_DEFINED
+
 #include "SkOpContour.h"
 #include "SkOpSegment.h"
 #include "SkPath.h"
@@ -106,3 +109,5 @@ public:
 private:
     SkOpSegment* fSegment;
 };
+
+#endif

src/pathops/SkPathOpsTSect.h

@@ -4,6 +4,8 @@
  * Use of this source code is governed by a BSD-style license that can be
  * found in the LICENSE file.
  */
+#ifndef SkPathOpsTSect_DEFINED
+#define SkPathOpsTSect_DEFINED
 
 #include "SkChunkAlloc.h"
 #include "SkPathOpsBounds.h"
@@ -2241,3 +2243,5 @@ void SkTSect<TCurve, OppCurve>::BinarySearch(SkTSect<TCurve, OppCurve>* sect1,
     }
     SkASSERT(intersections->used() <= TCurve::kMaxIntersections);
 }
+
+#endif