Port virtual time to InspectorAgentState fields.

This is a refactoring except for
kVirtualTimeTaskStarvationCount. Previously, the code
called state_->setDouble(...VirtualTimeTaskStarvationCount, ...);
but then read it as an int, so it basically wouldn't get saved.
Now it's always an int.

Bug: 851762
Change-Id: I288274ddddc44c910d89ef1fb8c1a6eacd54d8c5
Reviewed-on: https://chromium-review.googlesource.com/1161329
Commit-Queue: Johannes Henkel <johannes@chromium.org>
Reviewed-by: Andrey Kosyakov <caseq@chromium.org>
Cr-Commit-Position: refs/heads/master@{#580644}

third_party/blink/renderer/core/inspector/inspector_emulation_agent.h

@@ -132,6 +132,13 @@ class CORE_EXPORT InspectorEmulationAgent final
   InspectorAgentState::String navigator_platform_override_;
   InspectorAgentState::String user_agent_override_;
   InspectorAgentState::String accept_language_override_;
+  InspectorAgentState::Double virtual_time_budget_;
+  InspectorAgentState::Double virtual_time_budget_initial_offset_;
+  InspectorAgentState::Double initial_virtual_time_;
+  InspectorAgentState::Double virtual_time_offset_;
+  InspectorAgentState::String virtual_time_policy_;
+  InspectorAgentState::Integer virtual_time_task_starvation_count_;
+  InspectorAgentState::Boolean wait_for_navigation_;
   DISALLOW_COPY_AND_ASSIGN(InspectorEmulationAgent);
 };