3 files changed, 35 insertions, 6 deletions
diff --git a/tools/ok_vias.cpp b/tools/ok_vias.cpp
index b7fd2fef13..35e6f1fcab 100644
--- a/tools/ok_vias.cpp
+++ b/tools/ok_vias.cpp
@@ -5,6 +5,7 @@
  * found in the LICENSE file.
  */
 
+#include "SkEventTracingPriv.h"
 #include "SkImage.h"
 #include "SkOSFile.h"
 #include "SkPictureRecorder.h"
@@ -186,3 +187,28 @@ struct Memory : Dst {
     }
 };
 static Register memory{"memory", "print process maximum memory usage", Memory::Create};
+
+static SkOnce init_tracing_once;
+struct Trace : Dst {
+    std::unique_ptr<Dst> target;
+    std::string trace_mode;
+
+    static std::unique_ptr<Dst> Create(Options options, std::unique_ptr<Dst> dst) {
+        Trace via;
+        via.target = std::move(dst);
+        via.trace_mode = options("mode", "trace.json");
+        return move_unique(via);
+    }
+
+    Status draw(Src* src) override {
+        init_tracing_once([&] { initializeEventTracingForTools(trace_mode.c_str()); });
+        return target->draw(src);
+    }
+
+    sk_sp<SkImage> image() override {
+        return target->image();
+    }
+};
+static Register trace {"trace",
+                       "enable tracing in mode=atrace, mode=debugf, or mode=trace.json",
+                       Trace::Create};
diff --git a/tools/trace/SkEventTracingPriv.cpp b/tools/trace/SkEventTracingPriv.cpp
index 783cfeaa32..42d992cb13 100644
--- a/tools/trace/SkEventTracingPriv.cpp
+++ b/tools/trace/SkEventTracingPriv.cpp
@@ -22,12 +22,14 @@ DEFINE_string(trace, "",
               "               trace events to specified file as JSON, for viewing\n"
               "               with chrome://tracing");
 
-void initializeEventTracingForTools() {
-    if (FLAGS_trace.isEmpty()) {
-        return;
+void initializeEventTracingForTools(const char* traceFlag) {
+    if (!traceFlag) {
+        if (FLAGS_trace.isEmpty()) {
+            return;
+        }
+        traceFlag = FLAGS_trace[0];
     }
 
-    const char* traceFlag = FLAGS_trace[0];
     SkEventTracer* eventTracer = nullptr;
     if (0 == strcmp(traceFlag, "atrace")) {
         eventTracer = new SkATrace();
diff --git a/tools/trace/SkEventTracingPriv.h b/tools/trace/SkEventTracingPriv.h
index aa3ee6d4d9..fb7b2f3fa5 100644
--- a/tools/trace/SkEventTracingPriv.h
+++ b/tools/trace/SkEventTracingPriv.h
@@ -11,9 +11,10 @@
 #include "SkMutex.h"
 
 /**
- * Construct and install an SkEventTracer, based on the 'trace' command line argument.
+ * Construct and install an SkEventTracer, based on the mode,
+ * defaulting to the --trace command line argument.
  */
-void initializeEventTracingForTools();
+void initializeEventTracingForTools(const char* mode = nullptr);
 
 /**
  * Helper class used by internal implementations of SkEventTracer to manage categories.