Revert of android: Make dex_action.gypi not call md5sum. (https://codereview.chromium.org/183883024/)

Reason for revert:
Experimentally reverting because it is possible that this CL broke the android build http://build.chromium.org/p/chromium/builders/Android/builds/21418/steps/compile/logs/stdio

Will undo the revert if this CL is innocent

Original issue's description:
> android: Make dex_action.gypi not call md5sum.
> 
> No intended behavior change.
> 
> dex_action.gypi didn't pass its input_paths variable to dex.py,
> but that was only set in a single place, and only to a single file there.
> It was only used in java_apk.gypi which does manual threading of
> stamp files to order actions (since it's a gypi, it can't easily use type
> none targets with dependencies). Since dex.py doesn't look at this
> stamp file at all, the it doesn't need to rerun when the stamp file disappears.
> 
> To make this a bit more obvious, remove dex_action.gypi's input_paths
> variable and set 'inputs' directly in the one place with the stamp file.
> (dex.py will still rerun if the name of the stamp file changes, due to
> regular timestamp handling.)
> 
> BUG=177552
> NOTRY=true
> 
> Committed: https://src.chromium.org/viewvc/chrome?view=rev&revision=255325

TBR=cjhopman@chromium.org,thakis@chromium.org
NOTREECHECKS=true
NOTRY=true
BUG=177552

Review URL: https://codereview.chromium.org/185563012

git-svn-id: svn://svn.chromium.org/chrome/trunk/src@255356 0039d316-1c4b-4281-b951-d872f2087c98
SVN changes up to revision 255356