rebaseline_server: use new intermediate JSON format

gm/rebaseline_server/imagediffdb.py

Index: gm/rebaseline_server/imagediffdb.py
diff --git a/gm/rebaseline_server/imagediffdb.py b/gm/rebaseline_server/imagediffdb.py
index 8cec46bc9434fcb74ee7d1b1d2619e0411704618..e2608e2d866d4d54eef884b8483c14f116861b23 100644
--- a/gm/rebaseline_server/imagediffdb.py
+++ b/gm/rebaseline_server/imagediffdb.py
@@ -43,6 +43,14 @@ WHITEDIFFS_SUBDIR = 'whitediffs'
 
 VALUES_PER_BAND = 256
 
+# Keys used within DiffRecord dictionary representations.
+# Keep these in sync with static/constants.js
+KEY__DIFFERENCE_DATA__MAX_DIFF_PER_CHANNEL = 'maxDiffPerChannel'
+KEY__DIFFERENCE_DATA__NUM_DIFF_PIXELS = 'numDifferingPixels'
+KEY__DIFFERENCE_DATA__PERCENT_DIFF_PIXELS = 'percentDifferingPixels'
+KEY__DIFFERENCE_DATA__PERCEPTUAL_DIFF = 'perceptualDifference'
+KEY__DIFFERENCE_DATA__WEIGHTED_DIFF = 'weightedDiffMeasure'
+
 
 class DiffRecord(object):
   """ Record of differences between two images. """
@@ -186,10 +194,12 @@ class DiffRecord(object):
     """Returns a dictionary representation of this DiffRecord, as needed when
     constructing the JSON representation."""
     return {
-        'numDifferingPixels': self._num_pixels_differing,
-        'percentDifferingPixels': self.get_percent_pixels_differing(),
-        'weightedDiffMeasure': self.get_weighted_diff_measure(),
-        'maxDiffPerChannel': self._max_diff_per_channel,
+        KEY__DIFFERENCE_DATA__NUM_DIFF_PIXELS: self._num_pixels_differing,
+        KEY__DIFFERENCE_DATA__PERCENT_DIFF_PIXELS:
+            self.get_percent_pixels_differing(),
+        KEY__DIFFERENCE_DATA__WEIGHTED_DIFF: self.get_weighted_diff_measure(),
+        KEY__DIFFERENCE_DATA__MAX_DIFF_PER_CHANNEL: self._max_diff_per_channel,
+        KEY__DIFFERENCE_DATA__PERCEPTUAL_DIFF: self._perceptual_difference,
     }
 
 
@@ -398,6 +408,9 @@ def _get_difference_locator(expected_image_locator, actual_image_locator):
   """Returns the locator string used to look up the diffs between expected_image
   and actual_image.
 
+  We must keep this function in sync with getImageDiffRelativeUrl() in
+  static/loader.js
+
   Args:
     expected_image_locator: locator string pointing at expected image
     actual_image_locator: locator string pointing at actual image