BlendTest: implicit casts -> explicit casts

BUG=skia:
R=reed@google.com, mtklein@google.com

Author: mtklein@chromium.org

Review URL: https://codereview.chromium.org/181503003

git-svn-id: http://skia.googlecode.com/svn/trunk@13595 2bbb7eff-a529-9590-31e7-b0007b416f81
diff --git a/tests/BlendTest.cpp b/tests/BlendTest.cpp
index 9b42e56..b72d8d5 100644
--- a/tests/BlendTest.cpp
+++ b/tests/BlendTest.cpp
@@ -10,7 +10,7 @@
 // This is our golden algorithm.
 static uint8_t blend_double_round(uint8_t dst, uint8_t src, uint8_t srcAlpha) {
     SkASSERT(src <= srcAlpha);
-    return 0.5 + src + dst * (255.0 - srcAlpha) / 255.0;
+    return SkToU8(0.5 + src + dst * (255.0 - srcAlpha) / 255.0);
 }
 
 static uint8_t abs_diff(uint8_t a, uint8_t b) {
@@ -52,15 +52,15 @@
 }
 
 static uint8_t blend_double_trunc(uint8_t dst, uint8_t src, uint8_t srcAlpha) {
-    return src + dst * (255.0 - srcAlpha) / 255.0;
+    return SkToU8(src + dst * (255.0 - srcAlpha) / 255.0);
 }
 
 static uint8_t blend_float_trunc(uint8_t dst, uint8_t src, uint8_t srcAlpha) {
-    return src + dst * (255.0f - srcAlpha) / 255.0f;
+    return SkToU8(src + dst * (255.0f - srcAlpha) / 255.0f);
 }
 
 static uint8_t blend_float_round(uint8_t dst, uint8_t src, uint8_t srcAlpha) {
-    return 0.5f + src + dst * (255.0f - srcAlpha) / 255.0f;
+    return SkToU8(0.5f + src + dst * (255.0f - srcAlpha) / 255.0f);
 }
 
 static uint8_t blend_255_trunc(uint8_t dst, uint8_t src, uint8_t srcAlpha) {