Rollback of commit 59180a4.

*** Reason for rollback ***

Break bazel-tests and many other jobs on CI.
http://ci.bazel.io/job/bazel-tests/BAZEL_VERSION=HEAD,PLATFORM_NAME=linux-x86_64/651/console

*** Original change description ***

Add SpawnInputExpander helper class to arrange runfiles for spawn strategies

This new class is a combination of SpawnHelper and our internal code; the
plan is to migrate all spawn strategies to the new class. The strict flag
should be enabled by default, but that's a breaking change, so we need to do
it later.

- Use it in SandboxStrategy.
- Add ActionInput.getExecPath to return a PathFragment; this avoids lots of
  back and forth between path fragments and strings.

This is a step towards #159...

***

--
PiperOrigin-RevId: 150610616
MOS_MIGRATED_REVID=150610616

src/main/java/com/google/devtools/build/lib/actions/ActionInput.java

@@ -14,8 +14,6 @@
 
 package com.google.devtools.build.lib.actions;
 
-import com.google.devtools.build.lib.vfs.PathFragment;
-
 /**
  * Represents an input file to a build action, with an appropriate relative path and digest
  * value.
@@ -34,13 +32,6 @@
  */
 public interface ActionInput {
 
-  /**
-   * @return the relative path to the input file.
-   */
-  String getExecPathString();
-
-  /**
-   * @return the relative path to the input file.
-   */
-  PathFragment getExecPath();
+  /** @return the relative path to the input file. */
+  public String getExecPathString();
 }

src/main/java/com/google/devtools/build/lib/actions/ActionInputHelper.java

@@ -69,7 +69,6 @@ public void expand(Artifact mm, Collection<? super Artifact> output) {
    */
   private static class BasicActionInput implements ActionInput {
     private final String path;
-
     public BasicActionInput(String path) {
       this.path = Preconditions.checkNotNull(path);
     }
@@ -79,11 +78,6 @@ public String getExecPathString() {
       return path;
     }
 
-    @Override
-    public PathFragment getExecPath() {
-      return new PathFragment(path);
-    }
-
     @Override
     public int hashCode() {
       return path.hashCode();

src/main/java/com/google/devtools/build/lib/actions/Artifact.java

@@ -344,7 +344,6 @@ public final Root getRoot() {
     return root;
   }
 
-  @Override
   public final PathFragment getExecPath() {
     return execPath;
   }

src/main/java/com/google/devtools/build/lib/analysis/Runfiles.java

@@ -134,8 +134,8 @@ private static final class SymlinkEntry implements SkylarkValue {
     private final Artifact artifact;
 
     private SymlinkEntry(PathFragment path, Artifact artifact) {
-      this.path = Preconditions.checkNotNull(path);
-      this.artifact = Preconditions.checkNotNull(artifact);
+      this.path = path;
+      this.artifact = artifact;
     }
 
     public PathFragment getPath() {
@@ -146,12 +146,10 @@ public Artifact getArtifact() {
       return artifact;
     }
 
-    @Override
     public boolean isImmutable() {
       return true;
     }
 
-    @Override
     public void write(Appendable buffer, char quotationMark) {
       Printer.append(buffer, "SymlinkEntry(path = ");
       Printer.write(buffer, getPath().toString(), quotationMark);
@@ -433,11 +431,11 @@ static Map<PathFragment, Artifact> filterListForObscuringSymlinks(
    * Returns the symlinks as a map from PathFragment to Artifact.
    *
    * @param eventHandler Used for throwing an error if we have an obscuring runlink within the
-   *    normal source tree entries, or runfile conflicts. May be null, in which case obscuring
-   *    symlinks are silently discarded, and conflicts are overwritten.
+   *     normal source tree entries, or runfile conflicts. May be null, in which case obscuring
+   *     symlinks are silently discarded, and conflicts are overwritten.
    * @param location Location for eventHandler warnings. Ignored if eventHandler is null.
    * @return Map<PathFragment, Artifact> path fragment to artifact, of normal source tree entries
-   *    and elements that live outside the source tree. Null values represent empty input files.
+   *     and elements that live outside the source tree. Null values represent empty input files.
    */
   public Map<PathFragment, Artifact> getRunfilesInputs(EventHandler eventHandler, Location location)
       throws IOException {
@@ -852,13 +850,13 @@ public Builder addTransitiveArtifacts(NestedSet<Artifact> artifacts) {
      * Adds a symlink.
      */
     public Builder addSymlink(PathFragment link, Artifact target) {
+      Preconditions.checkNotNull(link);
+      Preconditions.checkNotNull(target);
       symlinksBuilder.add(new SymlinkEntry(link, target));
       return this;
     }
 
-    /**
-     * Adds several symlinks. Neither keys nor values may be null.
-     */
+    /** Adds several symlinks. */
     public Builder addSymlinks(Map<PathFragment, Artifact> symlinks) {
       for (Map.Entry<PathFragment, Artifact> symlink : symlinks.entrySet()) {
         symlinksBuilder.add(new SymlinkEntry(symlink.getKey(), symlink.getValue()));
@@ -878,13 +876,13 @@ public Builder addSymlinks(NestedSet<SymlinkEntry> symlinks) {
      * Adds a root symlink.
      */
     public Builder addRootSymlink(PathFragment link, Artifact target) {
+      Preconditions.checkNotNull(link);
+      Preconditions.checkNotNull(target);
       rootSymlinksBuilder.add(new SymlinkEntry(link, target));
       return this;
     }
 
-    /**
-     * Adds several root symlinks. Neither keys nor values may be null.
-     */
+    /** Adds several root symlinks. */
     public Builder addRootSymlinks(Map<PathFragment, Artifact> symlinks) {
       for (Map.Entry<PathFragment, Artifact> symlink : symlinks.entrySet()) {
         rootSymlinksBuilder.add(new SymlinkEntry(symlink.getKey(), symlink.getValue()));