[LayoutNG] Introduce block child iterator.

third_party/WebKit/Source/core/layout/ng/ng_block_break_token.h

Index: third_party/WebKit/Source/core/layout/ng/ng_block_break_token.h
diff --git a/third_party/WebKit/Source/core/layout/ng/ng_block_break_token.h b/third_party/WebKit/Source/core/layout/ng/ng_block_break_token.h
index 39e9f48b8789f14b0845a150edf281e8ea068fe3..dccf6ec37978b6cd281a2cf1a4207de30f1579f0 100644
--- a/third_party/WebKit/Source/core/layout/ng/ng_block_break_token.h
+++ b/third_party/WebKit/Source/core/layout/ng/ng_block_break_token.h
@@ -5,6 +5,7 @@
 #ifndef NGBlockBreakToken_h
 #define NGBlockBreakToken_h
 
+#include "core/CoreExport.h"
 #include "core/layout/ng/ng_break_token.h"
 #include "platform/LayoutUnit.h"
 
@@ -13,27 +14,20 @@ namespace blink {
 class NGBlockNode;
 
 // Represents a break token for a block node.
-class NGBlockBreakToken : public NGBreakToken {
+class CORE_EXPORT NGBlockBreakToken : public NGBreakToken {
  public:
   // Creates a break token for a node which did fragment, and can potentially
   // produce more fragments.
   NGBlockBreakToken(NGBlockNode* node,
                     LayoutUnit used_block_size,
-                    HeapVector<Member<NGBreakToken>>& child_break_tokens)
-      : NGBreakToken(kBlockBreakToken, /* is_finished */ false, node),
-        used_block_size_(used_block_size) {
-    child_break_tokens_.swap(child_break_tokens);
-  }
+                    HeapVector<Member<NGBreakToken>>& child_break_tokens);

[mstensho (USE GERRIT), 2017/02/22 13:11:30]

Since the implementation has now been moved to a separate file, better document
here that child_break_tokens are taken over and emptied.

[ikilpatrick, 2017/02/22 18:47:19]

Done.

 
   // Creates a break token for a node which cannot produce any more fragments.
-  explicit NGBlockBreakToken(NGBlockNode* node)
-      : NGBreakToken(kBlockBreakToken, /* is_finished */ true, node) {}
+  explicit NGBlockBreakToken(NGBlockNode* node);
 
   // TODO(ikilpatrick): Remove this constructor and break_offset once we've
   // switched to new multi-col approach.
-  NGBlockBreakToken(NGBlockNode* node, LayoutUnit break_offset)
-      : NGBreakToken(kBlockBreakToken, false, node),
-        break_offset_(break_offset) {}
+  NGBlockBreakToken(NGBlockNode* node, LayoutUnit break_offset);
 
   // Represents the amount of block size used in previous fragments.
   //