Add pre_log option to nanobench; make this option default true in nanobench_flags.py and dm_flags.py.

BUG=skia:4826
BUG=skia:4827
GOLD_TRYBOT_URL= https://gold.skia.org/search2?unt=true&query=source_type%3Dgm&master=false&issue=1612483002

Review URL: https://codereview.chromium.org/1612483002
diff --git a/tools/dm_flags.json b/tools/dm_flags.json
index 6fe4d3c..bf88638 100644
--- a/tools/dm_flags.json
+++ b/tools/dm_flags.json
@@ -1,5 +1,6 @@
 {
   "Pretend-iOS-Bot": [
+    "--pre_log", 
     "--matrix", 
     "0", 
     "1", 
@@ -375,6 +376,7 @@
     "image-cacherator-from-ctable"
   ], 
   "Test-Android-GCC-AndroidOne-GPU-Mali400MP2-Arm7-Release": [
+    "--pre_log", 
     "--config", 
     "565", 
     "8888", 
@@ -723,6 +725,7 @@
     "~WritePixels"
   ], 
   "Test-Android-GCC-GalaxyS3-GPU-Mali400-Arm7-Debug": [
+    "--pre_log", 
     "--config", 
     "565", 
     "8888", 
@@ -1074,6 +1077,7 @@
     "~WritePixels"
   ], 
   "Test-Android-GCC-GalaxyS4-GPU-SGX544-Arm7-Release": [
+    "--pre_log", 
     "--config", 
     "565", 
     "8888", 
@@ -1427,6 +1431,7 @@
     "~ReadPixels"
   ], 
   "Test-Android-GCC-Nexus7-GPU-Tegra3-Arm7-Release": [
+    "--pre_log", 
     "--config", 
     "565", 
     "8888", 
@@ -1772,6 +1777,7 @@
     "image-cacherator-from-ctable"
   ], 
   "Test-Android-GCC-Nexus9-GPU-TegraK1-Arm64-Debug": [
+    "--pre_log", 
     "--config", 
     "565", 
     "8888", 
@@ -2119,6 +2125,7 @@
     "image-cacherator-from-ctable"
   ], 
   "Test-Android-GCC-NexusPlayer-CPU-SSSE3-x86-Release": [
+    "--pre_log", 
     "--config", 
     "565", 
     "8888", 
@@ -2476,6 +2483,7 @@
     "~ResourceCache"
   ], 
   "Test-Mac10.8-Clang-MacMini4.1-CPU-SSE4-x86_64-Release": [
+    "--pre_log", 
     "--matrix", 
     "0", 
     "1", 
@@ -2848,6 +2856,7 @@
     "image-cacherator-from-ctable"
   ], 
   "Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-TSAN": [
+    "--pre_log", 
     "--matrix", 
     "0", 
     "1", 
@@ -3221,6 +3230,7 @@
     "image-cacherator-from-ctable"
   ], 
   "Test-Ubuntu-GCC-GCE-CPU-AVX2-x86_64-Release-Valgrind": [
+    "--pre_log", 
     "--matrix", 
     "0", 
     "1", 
@@ -3616,6 +3626,7 @@
     "~Threaded"
   ], 
   "Test-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-Valgrind": [
+    "--pre_log", 
     "--matrix", 
     "0", 
     "1", 
@@ -4006,6 +4017,7 @@
     "~Threaded"
   ], 
   "Test-Win7-MSVC-ShuttleA-GPU-HD2000-x86-Debug-ANGLE": [
+    "--pre_log", 
     "--matrix", 
     "0", 
     "1", 
diff --git a/tools/dm_flags.py b/tools/dm_flags.py
index 8d74450..be348bc 100755
--- a/tools/dm_flags.py
+++ b/tools/dm_flags.py
@@ -27,7 +27,7 @@
 
 cov_start = lineno()+1   # We care about coverage starting just past this def.
 def get_args(bot):
-  args = []
+  args = ['--pre_log']
 
   configs = ['565', '8888', 'gpu']
 
diff --git a/tools/flags/SkCommonFlags.cpp b/tools/flags/SkCommonFlags.cpp
index a2da131..2d5a855 100644
--- a/tools/flags/SkCommonFlags.cpp
+++ b/tools/flags/SkCommonFlags.cpp
@@ -48,3 +48,4 @@
 DEFINE_string(properties, "",
               "Space-separated key/value pairs to add to JSON identifying this run.");
 
+DEFINE_bool2(pre_log, p, false, "Log before running each test. May be incomprehensible when threading");
diff --git a/tools/flags/SkCommonFlags.h b/tools/flags/SkCommonFlags.h
index ddd8d3a..127d373 100644
--- a/tools/flags/SkCommonFlags.h
+++ b/tools/flags/SkCommonFlags.h
@@ -25,6 +25,7 @@
 DECLARE_bool(verbose);
 DECLARE_bool(veryVerbose);
 DECLARE_string(writePath);
+DECLARE_bool(pre_log);
 
 DECLARE_string(key);
 DECLARE_string(properties);
diff --git a/tools/nanobench_flags.json b/tools/nanobench_flags.json
index 1b44316..2ae91d0 100644
--- a/tools/nanobench_flags.json
+++ b/tools/nanobench_flags.json
@@ -1,5 +1,6 @@
 {
   "Perf-Android-GCC-NexusPlayer-GPU-PowerVR-x86-Release": [
+    "--pre_log", 
     "--images", 
     "--gpuStatsDump", 
     "true", 
@@ -42,6 +43,7 @@
     "~inc1.webp"
   ], 
   "Perf-Android-Nexus7-Tegra3-Arm7-Release": [
+    "--pre_log", 
     "--scales", 
     "1.0", 
     "1.1", 
@@ -79,6 +81,7 @@
     "~inc1.webp"
   ], 
   "Test-Android-GCC-GalaxyS4-GPU-SGX544-Arm7-Release": [
+    "--pre_log", 
     "--images", 
     "--gpuStatsDump", 
     "true", 
@@ -118,6 +121,7 @@
     "~inc1.webp"
   ], 
   "Test-Ubuntu-GCC-ShuttleA-GPU-GTX550Ti-x86_64-Release-Valgrind": [
+    "--pre_log", 
     "--images", 
     "--gpuStatsDump", 
     "true", 
@@ -164,6 +168,7 @@
     "~inc1.webp"
   ], 
   "Test-Win7-MSVC-ShuttleA-GPU-HD2000-x86-Debug-ANGLE": [
+    "--pre_log", 
     "--images", 
     "--gpuStatsDump", 
     "true", 
@@ -210,6 +215,7 @@
     "~inc1.webp"
   ], 
   "Test-iOS-Clang-iPad4-GPU-SGX554-Arm7-Debug": [
+    "--pre_log", 
     "--images", 
     "--gpuStatsDump", 
     "true", 
diff --git a/tools/nanobench_flags.py b/tools/nanobench_flags.py
index 9061372..685b302 100755
--- a/tools/nanobench_flags.py
+++ b/tools/nanobench_flags.py
@@ -27,7 +27,7 @@
 
 cov_start = lineno()+1   # We care about coverage starting just past this def.
 def get_args(bot):
-  args = []
+  args = ['--pre_log']
 
   if 'GPU' in bot:
     args.append('--images')