Initialize run_webkit_tests's image-first-tests flag from file

third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py

Index: third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
diff --git a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
index f999f5c9c19125cc61b0e1f10492326fa28b2d1f..4f3166961d2bcabd66fd4a42bab9e8ad8f73c2c9 100644
--- a/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
+++ b/third_party/WebKit/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
@@ -555,6 +555,10 @@ def _set_up_derived_options(port, options, args):
     if not options.seed:
         options.seed = port.host.time()
 
+    if not options.image_first_tests:
+        image_first_tests_path = port.host.filesystem.join(port.layout_tests_dir(), 'ImageFirstTests')
+        options.image_first_tests.extend(line for line in open(image_first_tests_path).read().strip().split('\n') if line)

[qyearsley, 2017/03/30 17:26:12]

In general, most of the code in webkitpy interacts with the filesystem
(including reading files) via a FileSystem object so that it can be replaced by
MockFileSystem in unit tests.

So for example, here would want to do something like:
    contents = port.host.filesystem.read_text_file(image_first_tests_path)
    options.image_first_tests.extend(line for line in contents.splitlines(False)
if line)

Note, if there is extra whitespace at the beginning and end of lines (e.g.
"one\n  two \nthree\n") then it'll be kept, but I assume that's OK. If it's not,
then we could change it to:
options.image_first_tests.extend(line.strip() for line in lines if line.strip())

I think it's a good idea to add a simple test for this in
run_webkit_tests_unittest.py.

[Gleb Lanbin, 2017/03/30 23:45:39]

Done.

+
 
 def _run_tests(port, options, args, printer):
     _set_up_derived_options(port, options, args)