Stop running nanobench on Test.*Debug bots

tools/buildbot_spec.json

 {
   "Build-Mac10.8-Clang-Arm7-Debug-Android": {
     "build_targets": [
       "most"
     ], 
     "builder_cfg": {
       "compiler": "Clang", 
       "configuration": "Debug", 
       "extra_config": "Android", 
       "is_trybot": false, 
@@ skipping 3537 matching lines @@
       "~inc13.png", 
       "~inc14.png", 
       "~inc0.webp", 
       "~inc1.webp"
     ], 
     "upload_dm_results": true, 
     "upload_perf_results": false
   }, 
   "Test-Android-GCC-Nexus6-GPU-Adreno420-Arm7-Debug": {
     "build_targets": [
-      "dm", 
-      "nanobench"
+      "dm"
     ], 
     "builder_cfg": {
       "arch": "Arm7", 
       "compiler": "GCC", 
       "configuration": "Debug", 
       "cpu_or_gpu": "GPU", 
       "cpu_or_gpu_value": "Adreno420", 
       "is_trybot": false, 
       "model": "Nexus6", 
       "os": "Android", 
@@ skipping 238 matching lines @@
       ".RW2", 
       "_", 
       "image", 
       "_", 
       ".PEF", 
       "_", 
       "image", 
       "_", 
       ".SRW"
     ], 
-    "do_perf_steps": true, 
+    "do_perf_steps": false, 
     "do_test_steps": true, 
     "env": {
       "GYP_DEFINES": "skia_arch_type=arm skia_warnings_as_errors=0"
     }, 
     "nanobench_flags": [
       "--pre_log", 
       "--images", 
       "--gpuStatsDump", 
       "true", 
       "--useThermalManager", 
@@ skipping 36 matching lines @@
       "~inc14.png", 
       "~inc0.webp", 
       "~inc1.webp"
     ], 
     "product.board": "shamu", 
     "upload_dm_results": true, 
     "upload_perf_results": false
   }, 
   "Test-Mac-Clang-MacMini6.2-GPU-HD4000-x86_64-Debug-CommandBuffer": {
     "build_targets": [
-      "dm", 
-      "nanobench"
+      "dm"
     ], 
     "builder_cfg": {
       "arch": "x86_64", 
       "compiler": "Clang", 
       "configuration": "Debug", 
       "cpu_or_gpu": "GPU", 
       "cpu_or_gpu_value": "HD4000", 
       "extra_config": "CommandBuffer", 
       "is_trybot": false, 
       "model": "MacMini6.2", 
@@ skipping 243 matching lines @@
       ".RW2", 
       "_", 
       "image", 
       "_", 
       ".PEF", 
       "_", 
       "image", 
       "_", 
       ".SRW"
     ], 
-    "do_perf_steps": true, 
+    "do_perf_steps": false, 
     "do_test_steps": true, 
     "env": {
       "CC": "/usr/bin/clang", 
       "CXX": "/usr/bin/clang++", 
       "GYP_DEFINES": "skia_arch_type=x86_64 skia_clang_build=1 skia_command_buffer=1 skia_warnings_as_errors=0"
     }, 
     "nanobench_flags": [
       "--pre_log", 
       "--images", 
       "--gpuStatsDump", 
@@ skipping 747 matching lines @@
       "_", 
       "image-cacherator-from-ctable", 
       "serialize-8888", 
       "gm", 
       "_", 
       "image-cacherator-from-ctable", 
       "--match", 
       "~Once", 
       "~Shared"
     ], 
-    "do_perf_steps": true, 
+    "do_perf_steps": false, 
     "do_test_steps": true, 
     "env": {
       "GYP_DEFINES": "skia_arch_type=x86_64 skia_gpu=0 skia_warnings_as_errors=0"
     }, 
     "nanobench_flags": [
       "--pre_log", 
       "--scales", 
       "1.0", 
       "1.1", 
       "--config", 
@@ skipping 876 matching lines @@
       "~inc13.png", 
       "~inc14.png", 
       "~inc0.webp", 
       "~inc1.webp"
     ], 
     "upload_dm_results": true, 
     "upload_perf_results": false
   }, 
   "Test-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-Valgrind": {
     "build_targets": [
-      "dm", 
-      "nanobench"
+      "dm"
     ], 
     "builder_cfg": {
       "arch": "x86_64", 
       "compiler": "GCC", 
       "configuration": "Release", 
       "cpu_or_gpu": "GPU", 
       "cpu_or_gpu_value": "GTX550Ti", 
       "extra_config": "Valgrind", 
       "is_trybot": false, 
       "model": "ShuttleA", 
@@ skipping 250 matching lines @@
       "image", 
       "_", 
       ".PEF", 
       "_", 
       "image", 
       "_", 
       ".SRW", 
       "--match", 
       "~Threaded"
     ], 
-    "do_perf_steps": true, 
+    "do_perf_steps": false, 
     "do_test_steps": true, 
     "env": {
       "GYP_DEFINES": "skia_arch_type=x86_64 skia_release_optimization_level=1 skia_warnings_as_errors=0"
     }, 
     "nanobench_flags": [
       "--pre_log", 
       "--images", 
       "--gpuStatsDump", 
       "true", 
       "--scales", 
@@ skipping 1298 matching lines @@
       ".RW2", 
       "_", 
       "image", 
       "_", 
       ".PEF", 
       "_", 
       "image", 
       "_", 
       ".SRW"
     ], 
-    "do_perf_steps": true, 
+    "do_perf_steps": false, 
     "do_test_steps": true, 
     "env": {
       "CC": "/usr/bin/clang", 
       "CXX": "/usr/bin/clang++", 
       "GYP_DEFINES": "skia_arch_type=arm skia_clang_build=1 skia_os=ios skia_warnings_as_errors=0"
     }, 
     "nanobench_flags": [
       "--pre_log", 
       "--images", 
       "--gpuStatsDump", 
@@ skipping 39 matching lines @@
       "~inc12.png", 
       "~inc13.png", 
       "~inc14.png", 
       "~inc0.webp", 
       "~inc1.webp"
     ], 
     "upload_dm_results": true, 
     "upload_perf_results": false
   }
 }