Add ability to output ImageBaseGSUrl to render_picture and use in rebaseline server

gm/rebaseline_server/imagepair_test.py

Index: gm/rebaseline_server/imagepair_test.py
diff --git a/gm/rebaseline_server/imagepair_test.py b/gm/rebaseline_server/imagepair_test.py
index c82e4b59cd62e0a43de4083c194b7b43514e63a4..1e069a077dcf1032dbe12a7ef6a46a374656d023 100755
--- a/gm/rebaseline_server/imagepair_test.py
+++ b/gm/rebaseline_server/imagepair_test.py
@@ -21,6 +21,8 @@ import imagepair
 
 IMG_URL_BASE = ('http://chromium-skia-gm.commondatastorage.googleapis.com/'
                 'gm/bitmap-64bitMD5/')
+ALT_IMG_URL_BASE = ('http://chromium-skia-gm.commondatastorage.googleapis.com/'
+                    'test/gm/bitmap-64bitMD5/')
 
 
 class ImagePairTest(unittest.TestCase):
@@ -74,6 +76,8 @@ class ImagePairTest(unittest.TestCase):
                 'imageBUrl': 'arcofzorro/16206093933823793653.png',
                 'isDifferent': False,
             },
+            # baseurls of the two images:
+            (IMG_URL_BASE, ALT_IMG_URL_BASE),
         ],
 
         [
@@ -91,13 +95,15 @@ class ImagePairTest(unittest.TestCase):
                     'perceptualDifference': 0.06620300000000157,
                     'diffUrl': 'arcofzorro_16206093933823793653_png_png-vs-' +
                         'arcofzorro_13786535001616823825_png_png.png',
-                    'whiteDiffUrl': 'arcofzorro_16206093933823793653_png_png' + 
+                    'whiteDiffUrl': 'arcofzorro_16206093933823793653_png_png' +
                         '-vs-arcofzorro_13786535001616823825_png_png.png',
                 },
                 'imageAUrl': 'arcofzorro/16206093933823793653.png',
                 'imageBUrl': 'arcofzorro/13786535001616823825.png',
                 'isDifferent': True,
             },
+            # baseurls of the two images:
+            (IMG_URL_BASE, IMG_URL_BASE),
         ],
 
         [
@@ -141,6 +147,8 @@ class ImagePairTest(unittest.TestCase):
                     'gradients_degenerate_2pt/11198253335583713230.png',
                 'isDifferent': True,
             },
+            # baseurls of the two images:
+            (IMG_URL_BASE, IMG_URL_BASE),
         ],
 
         # Test fix for http://skbug.com/2368 -- how do we handle an ImagePair
@@ -171,6 +179,8 @@ class ImagePairTest(unittest.TestCase):
                 'imageBUrl': 'nonexistentDir/111111.png',
                 'isDifferent': True,
             },
+            # baseurls of the two images:
+            (IMG_URL_BASE, IMG_URL_BASE),
         ],
 
         # One of the two images is missing, but download_all_images=True so we
@@ -187,6 +197,8 @@ class ImagePairTest(unittest.TestCase):
                 'imageBUrl': 'arcofzorro/13786535001616823825.png',
                 'isDifferent': True,
             },
+            # baseurls of the two images:
+            (IMG_URL_BASE, IMG_URL_BASE),
         ],
 
     ]
@@ -195,7 +207,8 @@ class ImagePairTest(unittest.TestCase):
     for selftest in selftests:
       image_pair = imagepair.ImagePair(
           image_diff_db=db,
-          base_url=IMG_URL_BASE,
+          imageA_base_url=selftest[5][0],
+          imageB_base_url=selftest[5][1],
           imageA_relative_url=selftest[0],
           imageB_relative_url=selftest[1],
           expectations=selftest[2],