gistfile1.diff

diff --git a/Tools/Scripts/webkitpy/layout_tests/port/base.py b/Tools/Scripts/webkitpy/layout_tests/port/base.py
index a1bd5bf..4b6384e 100755
--- a/Tools/Scripts/webkitpy/layout_tests/port/base.py
+++ b/Tools/Scripts/webkitpy/layout_tests/port/base.py
@@ -1263,6 +1263,12 @@ class Port(object):
     def _supports_switching_pixel_tests_per_test(self):
         return False
 
+    def defines_pixel_test_directories(self):
+        return False
+
+    def pixel_test_directories(self):
+        raise NotImplementedError("Port.pixel_test_directories")
+
 
 class VirtualTestSuite(object):
     def __init__(self, name, base, args, tests=None):
diff --git a/Tools/Scripts/webkitpy/layout_tests/port/qt.py b/Tools/Scripts/webkitpy/layout_tests/port/qt.py
index dad36b4..6229365 100644
--- a/Tools/Scripts/webkitpy/layout_tests/port/qt.py
+++ b/Tools/Scripts/webkitpy/layout_tests/port/qt.py
@@ -188,3 +188,9 @@ class QtPort(WebKitPort):
 
     def _supports_switching_pixel_tests_per_test(self):
         return True
+
+    def defines_pixel_test_directories(self):
+        return True
+
+    def pixel_test_directories(self):
+        return ['compositing']
diff --git a/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py b/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
index 35a8657..4de7d2a 100755
--- a/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
+++ b/Tools/Scripts/webkitpy/layout_tests/run_webkit_tests.py
@@ -30,6 +30,7 @@
 # OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF SUCH DAMAGE.
 
 import errno
+import glob
 import logging
 import optparse
 import os
@@ -189,16 +190,22 @@ def _set_up_derived_options(port, options):
             warnings.append("--pixel-test-directories has no effect without --pixel-tests")
             options.pixel_test_directories = []
         else:
-            sanitized = []
-            for directory in options.pixel_test_directories:
-                relative_path = port.relative_test_path_from_layout_tests_dir(directory)
-                if not os.path.isdir(os.path.join(port.layout_tests_dir(), relative_path)):
-                    warnings.append("--pixel-test-directories expects list of directories but got: " + directory)
-                else:
-                    sanitized.append(relative_path)
-
-            options.pixel_test_directories = list(set(sanitized))
-
+            if 'all' in options.pixel_test_directories:
+                options.pixel_test_directories = [directory for directory in glob.glob(port.layout_test_dir(), '*')
+                                                                if os.path.isdir(directory)]
+            else:
+                sanitized = []
+                for directory in options.pixel_test_directories:
+                    relative_path = port.relative_test_path_from_layout_tests_dir(directory)
+                    if not os.path.isdir(os.path.join(port.layout_tests_dir(), relative_path)):
+                        warnings.append("--pixel-test-directories expects list of directories but got: " + directory)
+                    else:
+                        sanitized.append(relative_path)
+
+                options.pixel_test_directories = list(set(sanitized))
+
+    elif port.defines_pixel_test_directories():
+        options.pixel_test_directories = por.pixel_test_directories()
 
     return warnings