Pass --images '' to nanobench to disable image benchmarking.

Enabling image benchmarking has caused most nanobench runs to fail,
both Debug and Release.

BUG=skia:3418
NOTREECHECKS=true
TBR=scroggo@google.com

Review URL: https://codereview.chromium.org/1381703003

tools/nanobench_flags.json

@@ -1,5 +1,6 @@
 {
   "Perf-Android-GCC-NexusPlayer-GPU-PowerVR-x86-Release": [
+    "--images", 
     "--scales", 
     "1.0", 
     "1.1", 
@@ -17,6 +18,7 @@
     "~desk_unicodetable"
   ], 
   "Perf-Android-Nexus7-Tegra3-Arm7-Release": [
+    "--images", 
     "--scales", 
     "1.0", 
     "1.1", 
@@ -35,6 +37,7 @@
     "~desk_carsvg"
   ], 
   "Test-Android-GCC-GalaxyS4-GPU-SGX544-Arm7-Release": [
+    "--images", 
     "--scales", 
     "1.0", 
     "1.1", 
@@ -52,6 +55,7 @@
     "~GLInstancedArraysBench"
   ], 
   "Test-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-Valgrind": [
+    "--images", 
     "--scales", 
     "1.0", 
     "1.1", 
@@ -70,6 +74,7 @@
     "1"
   ], 
   "Test-Win7-MSVC-ShuttleA-GPU-HD2000-x86-Debug-ANGLE": [
+    "--images", 
     "--scales", 
     "1.0", 
     "1.1", 
@@ -91,6 +96,7 @@
     "~etc1bitmap"
   ], 
   "Test-iOS-Clang-iPad4-GPU-SGX554-Arm7-Debug": [
+    "--images", 
     "--scales", 
     "1.0", 
     "1.1", 

tools/nanobench_flags.py

@@ -29,6 +29,9 @@ cov_start = lineno()+1   # We care about coverage starting just past this def.
 def get_args(bot):
   args = []
 
+  # Temporarily disable image benchmarking.
+  args.append('--images')
+
   if 'Appurify' not in bot:
     args.extend(['--scales', '1.0', '1.1'])