grit: Add fallback_to_default_layout attribute to <output>

grit/gather/chrome_scaled_image_unittest.py

Index: grit/gather/chrome_scaled_image_unittest.py
diff --git a/grit/gather/chrome_scaled_image_unittest.py b/grit/gather/chrome_scaled_image_unittest.py
index 957326edc02bf465fb250e6f73410061e9c8dd0e..4b0bbfcccd5ee248fd3692145f04ad750591fb26 100644
--- a/grit/gather/chrome_scaled_image_unittest.py
+++ b/grit/gather/chrome_scaled_image_unittest.py
@@ -79,11 +79,12 @@ def _If(expr, *body):
   return '<if expr="%s">\n%s\n</if>' % (expr, '\n'.join(body))
 
 
-def _RunBuildTest(self, structures, inputs, expected_outputs, skip_rc=False):
-  outputs = '\n'.join('<output filename="out/%s%s" type="%s" context="%s" />'
-                              % (context, ext, type, context)
+def _RunBuildTest(self, structures, inputs, expected_outputs, skip_rc=False, layout_fallback=''):
+  outputs = '\n'.join('<output filename="out/%s%s" type="%s" context="%s"%s />'
+                              % (context, ext, type, context, layout_fallback)
                       for ext, type in _OUTFILETYPES
                       for context in expected_outputs)
+
   infiles = {
     'in/in.grd': '''<?xml version="1.0" encoding="UTF-8"?>
       <grit latest_public_release="0" current_release="1">
@@ -172,3 +173,21 @@ class ChromeScaledImageUnittest(unittest.TestCase):
             ),
             {},  # no files
             {'tactile_123_percent': 'should fail before using this'})
+
+  def testNoFallbackToDefaultLayout(self):
+    d123a = _MakePNG([('AbCd', '')])
+    t123a = _MakePNG([('EfGh', '')])
+    d123b = _MakePNG([('IjKl', '')])
+    _RunBuildTest(self,
+        _Structures(None,
+            _Structure('IDR_A', 'a.png'),
+            _Structure('IDR_B', 'b.png'),
+        ),
+        {'default_123_percent/a.png': d123a,
+         'tactile_123_percent/a.png': t123a,
+         'default_123_percent/b.png': d123b,
+        },
+        {'default_123_percent': set([d123a, d123b]),
+         'tactile_123_percent': set([t123a]),

[flackr, 2015/06/23 13:33:33]

It looks like expected_output only verifies that everything specified is in the
pak, but for this test we want to verify that no extra resources from the base
pak are in the tactile pak.

[tdanderson, 2015/06/23 14:22:55]

I believe that's what we're doing. The check in _RunBuildTest() at line 112 is
for equality, and the tactile pak should contain only one png (t123a). If
fallback_to_default_layout="false" were not specified, then the tactile pak
would also contain d123b (see testNormalFallback()).

+        },
+        layout_fallback=' fallback_to_default_layout="false"')

[tdanderson, 2015/06/22 23:33:20]

todo in next patch set in this cl: generate this string similar to
_MakeFallbackAttr() and test that fallback happens as expected if
fallback_to_default_layout is explicitly set to "true"