Add "create_bundle" target in order to support bundle with gn.

tools/gn/function_toolchain.cc

Index: tools/gn/function_toolchain.cc
diff --git a/tools/gn/function_toolchain.cc b/tools/gn/function_toolchain.cc
index 9eeae982cf3bf17210ef53e4325d23b69c7f98a1..727be54d7362ddc85e3d4b125ef77aff8f5974c7 100644
--- a/tools/gn/function_toolchain.cc
+++ b/tools/gn/function_toolchain.cc
@@ -407,6 +407,10 @@ const char kTool_Help[] =
     "      \"stamp\": Tool for creating stamp files\n"
     "      \"copy\": Tool to copy files.\n"
     "\n"
+    "    Platform specific tools:\n"
+    "      \"copy_bundle_data\": [iOS, OS X] Tool to copy files in a bundle.\n"
+    "      \"compile_xcassets\": [iOS, OS X] Tool to compile asset catalogs.\n"
+    "\n"
     "Tool variables\n"
     "\n"
     "    command  [string with substitutions]\n"
@@ -718,6 +722,18 @@ const char kTool_Help[] =
     "  {{source}} which is the source of the copy. The stamp tool allows\n"
     "  only the common tool substitutions.\n"
     "\n"
+    "  The copy_bundle_data and compile_xcassets tools only allows the common\n"
+    "  tool substitutions. Both tools are required to create iOS/OS X bundles\n"
+    "  and need only be defined on those platforms.\n"
+    "\n"
+    "  The copy_bundle_data tool will be called with one source and needs to\n"
+    "  copy (optionally optimizing the data representation) to its output. It\n"
+    "  may be called with a directory as input and it needs to be recursively\n"
+    "  copied.\n"
+    "\n"
+    "  The compile_xcassets tool will be called with one or more source (each\n"
+    "  an asset catalog) that needs to be compiled to a single output.\n"
+    "\n"
     "Separate linking and dependencies for shared libraries\n"
     "\n"
     "  Shared libraries are special in that not all changes to them require\n"
@@ -812,9 +828,13 @@ Value RunTool(Scope* scope,
   } else if (IsLinkerTool(tool_type)) {
     subst_validator = &IsValidLinkerSubstitution;
     subst_output_validator = &IsValidLinkerOutputsSubstitution;
-  } else if (tool_type == Toolchain::TYPE_COPY) {
+  } else if (tool_type == Toolchain::TYPE_COPY ||
+             tool_type == Toolchain::TYPE_COPY_BUNDLE_DATA) {
     subst_validator = &IsValidCopySubstitution;
     subst_output_validator = &IsValidCopySubstitution;
+  } else if (tool_type == Toolchain::TYPE_COMPILE_XCASSETS) {
+    subst_validator = &IsValidCompileXCassetsSubstitution;
+    subst_output_validator = &IsValidCompileXCassetsSubstitution;
   } else {
     subst_validator = &IsValidToolSubstitution;
     subst_output_validator = &IsValidToolSubstitution;
@@ -851,9 +871,12 @@ Value RunTool(Scope* scope,
     return Value();
   }
 
-  if (tool_type != Toolchain::TYPE_COPY && tool_type != Toolchain::TYPE_STAMP) {
-    // All tools except the copy and stamp tools should have outputs. The copy
-    // and stamp tool's outputs are generated internally.
+  if (tool_type != Toolchain::TYPE_COPY &&
+      tool_type != Toolchain::TYPE_STAMP &&
+      tool_type != Toolchain::TYPE_COPY_BUNDLE_DATA &&
+      tool_type != Toolchain::TYPE_COMPILE_XCASSETS) {
+    // All tools should have outputs, except the copy, stamp, copy_bundle_data
+    // and compile_xcassets tools that generate their outputs internally.
     if (!ReadOutputs(&block_scope, function, subst_output_validator,
                      tool.get(), err))
       return Value();