disable some poppler tests due to flakiness (see bug)

expectations/gm/Test-Mac10.6-MacMini4.1-GeForce320M-x86_64-Release/expected-results.json

Index: expectations/gm/Test-Mac10.6-MacMini4.1-GeForce320M-x86_64-Release/expected-results.json
===================================================================
--- expectations/gm/Test-Mac10.6-MacMini4.1-GeForce320M-x86_64-Release/expected-results.json	(revision 11371)
+++ expectations/gm/Test-Mac10.6-MacMini4.1-GeForce320M-x86_64-Release/expected-results.json	(working copy)
@@ -7840,12 +7840,13 @@
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
-          2042594177985516213
+          18221340919266374351

[epoger, 2013/09/19 06:04:01]

rebaselined as follows:

tools/rebaseline.py --bugs 1643 --ignore-failure --unreviewed --configs
pdf-poppler --tests imageblur imagemagnifier giantbitmap_clamp_bilerp_scale

I guess the giantbitmap_clamp_bilerp_scale failure I noted in
https://code.google.com/p/skia/issues/detail?id=1643#c3 already "flaked back to
success".

         ]
       ], 
       "bugs": [
-        1578
+        1643
       ], 
+      "ignore-failure": true, 
       "reviewed-by-human": false
     }, 
     "imagefiltersbase_565.png": {
@@ -8034,12 +8035,13 @@
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
-          2042594177985516213
+          18221340919266374351
         ]
       ], 
       "bugs": [
-        1578
+        1643
       ], 
+      "ignore-failure": true, 
       "reviewed-by-human": false
     }, 
     "internal_links_565.png": {