Fix SkPaint::measureText for stroked hairline text

expectations/gm/Test-Ubuntu13.10-ShuttleA-NoGPU-x86_64-Debug/expected-results.json

 {
   "actual-results": {
     "failed": null, 
     "failure-ignored": null, 
     "no-comparison": null, 
     "succeeded": null
   }, 
   "expected-results": {
     "3x3bitmaprect_565.png": {
       "allowed-digests": [
@@ skipping 9193 matching lines @@
       ], 
       "ignore-failure": false
     }, 
     "shadertext2_pdf-poppler.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           5483462587049856153
         ]
       ], 
+      "ignore-failure": true,
       "reviewed-by-human": true
     }, 
     "shadertext3_565.png": {
       "allowed-digests": [
         [
           "bitmap-64bitMD5", 
           363651743109664983
         ]
       ], 
       "ignore-failure": false, 
@@ skipping 1630 matching lines @@
           "bitmap-64bitMD5", 
           12332625502817210303
         ]
       ], 
       "bugs": [
         1578
       ], 
       "reviewed-by-human": false
     }
   }
-}
+}