Fix typo "ReftPtr"

third_party/WebKit/Source/platform/wtf/PassRefPtr.h has a typo on line
47:
https://cs.chromium.org/chromium/src/third_party/WebKit/Source/platform/wtf/PassRefPtr.h?dr=CSs&l=47

"ReftPtr"

R=esprehn@chromium.org
BUG=706566

Review-Url: https://codereview.chromium.org/2780903005
Cr-Commit-Position: refs/heads/master@{#460595}

third_party/WebKit/Source/platform/wtf/PassRefPtr.h

@@ -44,7 +44,7 @@ inline void adopted(const void*) {}
 
 // requireAdoption() is not overloaded for WTF::RefCounted, which has a built-in
 // assumption that adoption is required. requireAdoption() is for bootstrapping
-// alternate reference count classes that are compatible with ReftPtr/PassRefPtr
+// alternate reference count classes that are compatible with RefPtr/PassRefPtr
 // but cannot have adoption checks enabled by default, such as skia's
 // SkRefCnt. The purpose of requireAdoption() is to enable adoption checks only
 // once it is known that the object will be used with RefPtr/PassRefPtr.