add FileChooser.SetUri and fix a memory leak of FileChooser.GetFilename

[lidaobing]

No description provided.

[codecov-io]

Codecov Report

Merging #370 into master will increase coverage by 1.22%.
The diff coverage is 100%.

@@            Coverage Diff            @@
##           master    #370      +/-   ##
=========================================
+ Coverage    3.75%   4.98%   +1.22%     
=========================================
  Files           1       1              
  Lines        4447    4477      +30     
=========================================
+ Hits          167     223      +56     
+ Misses       4275    4245      -30     
- Partials        5       9       +4

Impacted Files	Coverage Δ
gtk/gtk.go	4.98% <100%> (+1.22%)	⬆️

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[mattn]

please omit () Ah, this is C code. Sorry

[lidaobing]

@mattn I have run testcase about 20 times on my machine, and unfortunately the result is not consistent, sometimes the GetFilename() does not return as expected. sometimes it triggered a critical GTK warning in UnselectUri[1], I need some deep inspect in it. please do not merge, thanks.

[1]

(<unknown>:76378): Gtk-CRITICAL **: gtk_tree_selection_unselect_iter: assertion 'selection->tree_view->priv->model != NULL' failed
SIGTRAP: trace trap
PC=0x4f5cf07 m=0 sigcode=1
signal arrived during cgo execution

goroutine 9 [syscall, locked to thread]:
runtime.cgocall(0x4319720, 0xc42003fd00, 0xc42003fd28)
	/usr/local/Cellar/go/1.9.1/libexec/src/runtime/cgocall.go:132 +0xe4 fp=0xc42003fcd0 sp=0xc42003fc90 pc=0x400a204
github.com/mattn/go-gtk/gtk._Cfunc_gtk_file_chooser_unselect_uri(0x604d470, 0x560e380)
	github.com/mattn/go-gtk/gtk/_test/_obj_test/_cgo_gotypes.go:9200 +0x41 fp=0xc42003fd00 sp=0xc42003fcd0 pc=0x42c8531
github.com/mattn/go-gtk/gtk.(*FileChooser).UnselectUri.func1(0x604d470, 0x560e380)
	/Users/lidaobing/go/src/github.com/mattn/go-gtk/gtk/gtk.go:8162 +0x6a fp=0xc42003fd38 sp=0xc42003fd00 pc=0x42f749a
github.com/mattn/go-gtk/gtk.(*FileChooser).UnselectUri(0xc420010e28, 0xc42003fdc8, 0x1b)
	/Users/lidaobing/go/src/github.com/mattn/go-gtk/gtk/gtk.go:8162 +0x7a fp=0xc42003fd68 sp=0xc42003fd38 pc=0x42e2a9a
github.com/mattn/go-gtk/gtk_test.TestFILE_CHOOSER(0xc4200fc4b0)
	/Users/lidaobing/go/src/github.com/mattn/go-gtk/gtk/gtk_test.go:63 +0xa75 fp=0xc42003ffa8 sp=0xc42003fd68 pc=0x4312835
testing.tRunner(0xc4200fc4b0, 0x440ada8)
	/usr/local/Cellar/go/1.9.1/libexec/src/testing/testing.go:746 +0xd0 fp=0xc42003ffd0 sp=0xc42003ffa8 pc=0x40eb030
runtime.goexit()
	/usr/local/Cellar/go/1.9.1/libexec/src/runtime/asm_amd64.s:2337 +0x1 fp=0xc42003ffd8 sp=0xc42003ffd0 pc=0x4063b21
created by testing.(*T).Run
	/usr/local/Cellar/go/1.9.1/libexec/src/testing/testing.go:789 +0x2de

[lidaobing]

@mattn I remove the check in test, I think now you can merge.

[mattn]

okay, merging. thanks