Fix some noisy warnings on Windows x64.

src/core/SkDebug.cpp

Index: src/core/SkDebug.cpp
===================================================================
--- src/core/SkDebug.cpp	(revision 10215)
+++ src/core/SkDebug.cpp	(working copy)
@@ -11,38 +11,32 @@
 
 #ifdef SK_DEBUG
 
-int8_t SkToS8(long x)
-{
+int8_t SkToS8(intmax_t x) {
     SkASSERT((int8_t)x == x);
     return (int8_t)x;
 }
 
-uint8_t SkToU8(size_t x)
-{
+uint8_t SkToU8(uintmax_t x) {
     SkASSERT((uint8_t)x == x);
     return (uint8_t)x;
 }
 
-int16_t SkToS16(long x)
-{
+int16_t SkToS16(intmax_t x) {
     SkASSERT((int16_t)x == x);
     return (int16_t)x;
 }
 
-uint16_t SkToU16(size_t x)
-{
+uint16_t SkToU16(uintmax_t x) {
     SkASSERT((uint16_t)x == x);
     return (uint16_t)x;
 }
 
-int32_t SkToS32(long x)
-{
+int32_t SkToS32(intmax_t x) {
     SkASSERT((int32_t)x == x);
     return (int32_t)x;
 }
 
-uint32_t SkToU32(size_t x)
-{
+uint32_t SkToU32(uintmax_t x) {
     SkASSERT((uint32_t)x == x);
     return (uint32_t)x;
 }