nanobench: split CPU and GPU .SKP tile sizes.

Let's make CPU-bound .SKP benching mimic Chrome's tiles.
Unfortunately, the CPU code also performs a lot better with those big wide tiles...

BUG=skia:

Review URL: https://codereview.chromium.org/1189863002
diff --git a/tools/nanobench_flags.json b/tools/nanobench_flags.json
index e90f217..90002a8 100644
--- a/tools/nanobench_flags.json
+++ b/tools/nanobench_flags.json
@@ -63,12 +63,34 @@
     "hwui", 
     "msaa16", 
     "nvprmsaa16", 
-    "--benchTileW", 
+    "--GPUbenchTileW", 
     "256", 
-    "--benchTileH", 
+    "--GPUbenchTileH", 
     "256", 
     "--match", 
     "~gradient", 
     "~etc1bitmap"
+  ], 
+  "Test-iOS-Clang-iPad4-GPU-SGX554-Arm7-Debug": [
+    "--scales", 
+    "1.0", 
+    "1.1", 
+    "--skps", 
+    "ignore_skps", 
+    "--config", 
+    "565", 
+    "8888", 
+    "gpu", 
+    "nonrendering", 
+    "angle", 
+    "hwui", 
+    "msaa16", 
+    "nvprmsaa16", 
+    "--match", 
+    "~blurroundrect", 
+    "~patch_grid", 
+    "~desk_carsvg", 
+    "~keymobi", 
+    "~path_hairline"
   ]
 }
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