Apply snake_case to generated ColorData.cpp.

This CL has no behavior changes.

Bug: 770603
Change-Id: Ieaeec84b67a6a4dbb0063e43478def41b909448f
Reviewed-on: https://chromium-review.googlesource.com/961183
Commit-Queue: Koji Ishii <kojii@chromium.org>
Reviewed-by: Koji Ishii <kojii@chromium.org>
Cr-Commit-Position: refs/heads/master@{#543010}

third_party/WebKit/Source/platform/BUILD.gn

@@ -69,12 +69,12 @@ action("runtime_enabled_features") {
 action("color_data") {
   script = "../build/scripts/gperf.py"
 
-  color_data_gperf = "ColorData.gperf"
+  color_data_gperf = "color_data.gperf"
   inputs = [
     color_data_gperf,
   ]
 
-  output_file = "$blink_platform_output_dir/ColorData.cpp"
+  output_file = "$blink_platform_output_dir/color_data.cc"
   outputs = [
     output_file,
   ]