Add a SandboxedSpawnActionContext interface and implementations for our sandboxed execution strategies.

--
MOS_MIGRATED_REVID=134054610
diff --git a/src/main/java/com/google/devtools/build/lib/sandbox/SandboxStrategy.java b/src/main/java/com/google/devtools/build/lib/sandbox/SandboxStrategy.java
index 7a12e9b..6b5c3ed 100644
--- a/src/main/java/com/google/devtools/build/lib/sandbox/SandboxStrategy.java
+++ b/src/main/java/com/google/devtools/build/lib/sandbox/SandboxStrategy.java
@@ -19,8 +19,8 @@
 import com.google.devtools.build.lib.actions.ActionExecutionContext;
 import com.google.devtools.build.lib.actions.EnvironmentalExecException;
 import com.google.devtools.build.lib.actions.ExecException;
+import com.google.devtools.build.lib.actions.SandboxedSpawnActionContext;
 import com.google.devtools.build.lib.actions.Spawn;
-import com.google.devtools.build.lib.actions.SpawnActionContext;
 import com.google.devtools.build.lib.analysis.BlazeDirectories;
 import com.google.devtools.build.lib.vfs.Path;
 import com.google.devtools.build.lib.vfs.PathFragment;
@@ -28,7 +28,7 @@
 import java.util.Map;
 
 /** Abstract common ancestor for sandbox strategies implementing the common parts. */
-abstract class SandboxStrategy implements SpawnActionContext {
+abstract class SandboxStrategy implements SandboxedSpawnActionContext {
 
   private final BlazeDirectories blazeDirs;
   private final boolean verboseFailures;