Introduce CommandEnvironment and pass it instead of BlazeRuntime.

The very long term plan is to make BlazeRuntime immutable, so that we can
run multiple commands in the same server.

--
MOS_MIGRATED_REVID=103080946
diff --git a/src/main/java/com/google/devtools/build/lib/runtime/BuildSummaryStatsModule.java b/src/main/java/com/google/devtools/build/lib/runtime/BuildSummaryStatsModule.java
index d0b70f1..337f97f 100644
--- a/src/main/java/com/google/devtools/build/lib/runtime/BuildSummaryStatsModule.java
+++ b/src/main/java/com/google/devtools/build/lib/runtime/BuildSummaryStatsModule.java
@@ -41,9 +41,9 @@
   private Reporter reporter;
 
   @Override
-  public void beforeCommand(BlazeRuntime runtime, Command command) {
-    this.reporter = runtime.getReporter();
-    this.eventBus = runtime.getEventBus();
+  public void beforeCommand(Command command, CommandEnvironment env) {
+    this.reporter = env.getReporter();
+    this.eventBus = env.getEventBus();
     eventBus.register(this);
   }