simplify default bookmaker command line

When bookmaker is run without arguments,
run all commands.

Allow SkCommandLineFlags to be set
programatically if
no arguments are passed in.

R=scroggo@google.com

Bug: skia:8518
Change-Id: I00697417ce45eaec880977ea872dd7de1fea63a0
Reviewed-on: https://skia-review.googlesource.com/c/166980
Reviewed-by: Cary Clark <caryclark@skia.org>
Commit-Queue: Cary Clark <caryclark@skia.org>
Auto-Submit: Cary Clark <caryclark@skia.org>
diff --git a/tools/flags/SkCommandLineFlags.h b/tools/flags/SkCommandLineFlags.h
index bf4a41e..693a5db 100644
--- a/tools/flags/SkCommandLineFlags.h
+++ b/tools/flags/SkCommandLineFlags.h
@@ -162,6 +162,10 @@
         }
 
         void set(int i, const char* str) {
+            if (i >= fStrings.count()) {
+                this->append(str);
+                return;
+            }
             fStrings[i].set(str);
         }