Control TaskScheduler initialization params in renderers via field trial.

components/task_scheduler_util/common/variations_util.h

Index: components/task_scheduler_util/common/variations_util.h
diff --git a/components/task_scheduler_util/common/variations_util.h b/components/task_scheduler_util/common/variations_util.h
index d18c1d214c73f46fc18fdb462244bbf0dd85338c..eaf68e6e8227bb3a837715c5f0ff6c7032bbe246 100644
--- a/components/task_scheduler_util/common/variations_util.h
+++ b/components/task_scheduler_util/common/variations_util.h
@@ -9,9 +9,14 @@
 #include <string>
 #include <vector>
 
+#include "base/strings/string_piece.h"
 #include "base/task_scheduler/scheduler_worker_pool_params.h"
 #include "base/threading/platform_thread.h"
 
+namespace base {
+class CommandLine;
+}
+
 namespace task_scheduler_util {
 
 struct SchedulerConstantWorkerPoolParams {
@@ -31,6 +36,19 @@ std::vector<base::SchedulerWorkerPoolParams> GetWorkerPoolParams(
         constant_worker_pool_params_vector,
     const std::map<std::string, std::string>& variation_params);
 
+// Adds key-value pairs from |variation_params| whose key start with
+// |key_prefix| to the --task-scheduler-variation-params switch of
+// |command_line|.
+void AddVariationParamsToCommandLine(
+    const std::map<std::string, std::string> variation_params,
+    base::StringPiece key_prefix,

[gab, 2016/12/12 17:33:33]

Since this is in task_scheduler/, can't it just always use "BrowserScheduler"
internally and not have it as a parameter?

[gab, 2017/01/05 18:40:05]

ping

[fdoray, 2017/01/06 17:29:03]

|prefix| determines which variation params are added to a child process command
line. For renderers, we use "Renderer"
https://codereview.chromium.org/2568793003/diff/80001/chrome/browser/chrome_c...
We never use "BrowserScheduler".

I removed the |variation_params| argument and replaced it with an internal call
to variations::GetVariationParams("BrowserScheduler", ...);

+    base::CommandLine* command_line);
+
+// Returns a map with key-value pairs read from the
+// --task-scheduler-variation-params switch of |command_line|.
+std::map<std::string, std::string> GetVariationParamsFromCommandLine(
+    const base::CommandLine& command_line);
+
 }  // namespace task_scheduler_util
 
 #endif  // COMPONENTS_TASK_SCHEDULER_UTIL_COMMON_VARIATIONS_UTIL_H_