Fuchsia: Don't call MakeAbsoluteFilePath() when resolving FILE_EXE path

Previously PathProviderFuchsia() was calling MakeAbsoluteFilePath(),
which requires blocking IO, so it was DCHECKing on threads where
blocking IO is not allowed. This issue was breaking debug builds of
content_shell. Since we package all binaries produced in chromium,
argv[0] is expected to contain full path to the binary, so it's not
necessary to call MakeAbsoluteFilePath().

Bug: 787020
Change-Id: I45637ac6402ff6da1993ec571ad719a28210e721
Reviewed-on: https://chromium-review.googlesource.com/1055681Reviewed-by: Scott Graham <scottmg@chromium.org>
Commit-Queue: Sergey Ulanov <sergeyu@chromium.org>
Cr-Commit-Position: refs/heads/master@{#557937}

base/base_paths_fuchsia.cc

@@ -36,11 +36,9 @@ bool PathProviderFuchsia(int key, FilePath* result) {
     case FILE_MODULE:
       NOTIMPLEMENTED();
       return false;
-    case FILE_EXE: {
-      *result = base::MakeAbsoluteFilePath(base::FilePath(
-          base::CommandLine::ForCurrentProcess()->GetProgram().AsUTF8Unsafe()));
+    case FILE_EXE:
+      *result = CommandLine::ForCurrentProcess()->GetProgram();
       return true;
-    }
     case DIR_SOURCE_ROOT:
       *result = GetPackageRoot();
       return true;