Reporters lcovonly and cobertura collect information for transpiled files instead of original ones

Hi all,

I currently use karma-coverage on a bigger webpack based project. The html reporter works just fine and shows the coverage information on the original source. However, the lcov and cobertura reporters report on the babel-transpiled items instead of this. There was already an issue about this problem at https://github.com/gotwarlost/istanbul/issues/571.

The problems author moved away from karma, which made lcov work correctly. Therefore I think that it might have to do with the karma-coverage plugin.

I am currently using https://github.com/weblogixx/react-webpack-template as a base (just adding lcovonly into the karma.conf.js coverage section).

Adjusted part of karma.conf.js:

``` javascript
coverageReporter: {
dir: 'coverage/',
watermarks: {
statements: [ 70, 80 ],
functions: [ 70, 80 ],
branches: [ 70, 80 ],
lines: [ 70, 80 ]
},
reporters: [
{ type: 'text' },
{
type: 'html',
subdir: 'html'
},
{
type: 'cobertura',
subdir: 'cobertura'
},
{
type: 'lcovonly',
subdir: 'lcov'
}
]
}
```

Output of lcovonly (example, paths stripped for better readability):

```
TN:
SF:PROJECTPATH/src/components/Main.js
FN:7,(anonymous_1)
FN:7,defineProperties
FN:7,(anonymous_3)
FN:21,_interopRequireDefault
FN:23,_classCallCheck
FN:25,_possibleConstructorReturn
FN:27,_inherits
FN:32,(anonymous_8)
FN:35,AppComponent
FN:43,render
FNF:10
FNH:10
FNDA:1,(anonymous_1)
FNDA:1,defineProperties
FNDA:1,(anonymous_3)
FNDA:3,_interopRequireDefault
FNDA:2,_classCallCheck
FNDA:2,_possibleConstructorReturn
FNDA:1,_inherits
FNDA:1,(anonymous_8)
FNDA:2,AppComponent
FNDA:2,render
```

and the following one for cobertura:

``` xml

PROJECTPATH

```

The text and html reporters get the correct values, so I can see the coverage in the generated reports correctly.

Start with the coverageReporter configuration in karma.conf.js and compare how the text/html reporters handle source paths with the lcovonly and cobertura reporters shown in the issue. Trace the plugin's reporter and source-map handling, then verify that both reports reference original source files rather than transpiled output.

Written by the indexing model from the issue text.