File size reporter on Windows

[fiddep]

Is this a bug report?

Yes

Did you try recovering your dependencies?

Yes

Which terms did you search for in User Guide?

windows, build, size

Environment

Environment:
 OS: Windows 10
 Node: 10.9.0
 Yarn: 1.9.4
 npm: 6.2.0
 Watchman: Not Found
 Xcode: N/A
 Android Studio: Not Found

Packages: (wanted => installed)
 react: ^16.4.2 => 16.4.2
 react-dom: ^16.4.2 => 16.4.2
 react-scripts: 1.1.5 => 1.1.5

Steps to Reproduce

1. create a fresh app
2. run yarn build
3. add stuff to any file
4. run yarn build

Expected Behavior

the output would show that the file size has increased if a previous build was present

Actual Behavior

Nothing else except the current filesize is show
Before: http://prntscr.com/kndf9p
After: http://prntscr.com/kndit2

Possible Solution

The issue seems to be related to Windows and its path delimiter.
Adding
.replace(/\\/g, '/')
in FileSizeReporter
Solves the problem and don't seem to cause any issues on other OS

Would happily submit a PR for this

[Timer]

Please send a PR! Thanks. 😄