Remove trailing whitespace.

Also adds a presubmit to prevent adding trailing whitespace to source
code in the future.

Change-Id: I41a4df81487f6f00aa19b188f0cac6a3377efde6
Reviewed-on: https://skia-review.googlesource.com/57380
Reviewed-by: Ravi Mistry <rmistry@google.com>
Reviewed-by: Mike Reed <reed@google.com>
Commit-Queue: Ben Wagner <bungeman@google.com>
diff --git a/tests/MatrixTest.cpp b/tests/MatrixTest.cpp
index da2ae35..6f7a14f 100644
--- a/tests/MatrixTest.cpp
+++ b/tests/MatrixTest.cpp
@@ -968,7 +968,7 @@
 // Test that all variants of maprect are correct.
 DEF_TEST(Matrix_maprects, r) {
     const SkScalar scale = 1000;
-    
+
     SkMatrix mat;
     mat.setScale(2, 3);
     mat.postTranslate(1, 4);
@@ -980,7 +980,7 @@
                                       rand.nextSScalar1() * scale,
                                       rand.nextSScalar1() * scale);
         SkRect dst[3];
-        
+
         mat.mapPoints((SkPoint*)&dst[0].fLeft, (SkPoint*)&src.fLeft, 2);
         dst[0].sort();
         mat.mapRect(&dst[1], src);