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/bench/HardStopGradientBench_SpecialHardStops.cpp b/bench/HardStopGradientBench_SpecialHardStops.cpp
index 0a9e23e..e987901 100644
--- a/bench/HardStopGradientBench_SpecialHardStops.cpp
+++ b/bench/HardStopGradientBench_SpecialHardStops.cpp
@@ -84,7 +84,7 @@
         };
 
         SkScalar* positions = fKind == Kind::k001 ? pos_001 :
-                              fKind == Kind::k011 ? pos_011 : 
+                              fKind == Kind::k011 ? pos_011 :
                                                     pos_centered;
 
         int count = fKind == Kind::kCentered ? 4 : 3;
@@ -109,7 +109,7 @@
     int      fW;
     int      fH;
     Kind     fKind;
-    SkPaint  fPaint; 
+    SkPaint  fPaint;
 };
 
 DEF_BENCH(return new HardStopGradientBench_SpecialHardStops(100, 100, Kind::k001););