Merge pull request #751 from yuslepukhin/return_noerror

Mmap reads should not return error if reading past file

port/win/env_win.cc

@@ -233,13 +233,14 @@ class WinMmapReadableFile : public RandomAccessFile {
                       char* scratch) const override {
     Status s;
 
-    if (offset + n > length_) {
+    if (offset > length_) {
       *result = Slice();
-      s = IOError(fileName_, EINVAL);
+      return IOError(fileName_, EINVAL);
-    } else {
+    } else if (offset + n > length_) {
+      n = length_ - offset;
+    }
     *result =
         Slice(reinterpret_cast<const char*>(mapped_region_) + offset, n);
-    }
     return s;
   }