Add SkDebugf trace event handler.

Also adds more trace events to GPU backend.

Change-Id: Ifa5f0cd4b1fd582f0cc30d37d9e6414dc498c75d
Reviewed-on: https://skia-review.googlesource.com/24622
Reviewed-by: Greg Daniel <egdaniel@google.com>
Commit-Queue: Brian Salomon <bsalomon@google.com>
diff --git a/BUILD.gn b/BUILD.gn
index f60c23b..2fac60e 100644
--- a/BUILD.gn
+++ b/BUILD.gn
@@ -1028,6 +1028,7 @@
       "tools",
       "tools/debugger",
       "tools/timer",
+      "tools/trace",
     ]
     sources = [
       "tools/AndroidSkDebugToStdOut.cpp",
@@ -1046,6 +1047,8 @@
       "tools/sk_tool_utils.cpp",
       "tools/sk_tool_utils_font.cpp",
       "tools/timer/Timer.cpp",
+      "tools/trace/SkDebugfTracer.cpp",
+      "tools/trace/SkDebugfTracer.h",
     ]
     libs = []
     if (is_ios) {