Only use 256x256 tiles on hd2000 nanobench bots

Initial experiments did show that the 256 tile size fixed the hd2000 win7
nanobot failures. However it did not have any effect on other bots, so this
change is to move back to the larger tile size on all bots expect for the
hd2000.

BUG=skia:

Review URL: https://codereview.chromium.org/1022083002
diff --git a/bench/SKPBench.cpp b/bench/SKPBench.cpp
index 8139eda..3f52179 100644
--- a/bench/SKPBench.cpp
+++ b/bench/SKPBench.cpp
@@ -10,8 +10,8 @@
 #include "SkMultiPictureDraw.h"
 #include "SkSurface.h"
 
-DEFINE_int32(benchTileW, 256, "Tile width  used for SKP playback.");
-DEFINE_int32(benchTileH, 256, "Tile height used for SKP playback.");
+DEFINE_int32(benchTileW, 1600, "Tile width  used for SKP playback.");
+DEFINE_int32(benchTileH, 512, "Tile height used for SKP playback.");
 
 SKPBench::SKPBench(const char* name, const SkPicture* pic, const SkIRect& clip, SkScalar scale,
                    bool useMultiPictureDraw)
diff --git a/tools/nanobench_flags.json b/tools/nanobench_flags.json
index c98c2e1..8a50d25 100644
--- a/tools/nanobench_flags.json
+++ b/tools/nanobench_flags.json
@@ -85,6 +85,10 @@
     "hwui", 
     "msaa16", 
     "nvprmsaa16", 
+    "--benchTileW", 
+    "256", 
+    "--benchTileH", 
+    "256", 
     "--match", 
     "~gradient", 
     "~etc1bitmap"
diff --git a/tools/nanobench_flags.py b/tools/nanobench_flags.py
index 81cd8ce..cbd5c84 100755
--- a/tools/nanobench_flags.py
+++ b/tools/nanobench_flags.py
@@ -45,6 +45,10 @@
     elif 'Valgrind_CPU' in bot:
       args.append('--nogpu')
 
+  if 'HD2000' in bot:
+    args.extend(['--benchTileW', '256'])
+    args.extend(['--benchTileH', '256'])
+
   match = []
   if 'Android' in bot:
     # Segfaults when run as GPU bench. Very large texture?