Move state machines to state_machines subdir

third_party/WebKit/Source/core/editing/BackspaceStateMachine.h

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #ifndef BackspaceStateMachine_h
 #define BackspaceStateMachine_h
 
 #include "core/CoreExport.h"
 #include "wtf/Allocator.h"
 #include "wtf/Noncopyable.h"
 #include "wtf/text/Unicode.h"
 
 namespace blink {
 
 class CORE_EXPORT BackspaceStateMachine {
     STACK_ALLOCATED();
     WTF_MAKE_NONCOPYABLE(BackspaceStateMachine);
 public:
+    enum class State {
+        Unknown, // Indicates the state machine is in unknown state.
+        NeedMoreCodeUnit, // Indicates the state machine needs more code units to transit the state.
+        NeedFollowingCodeUnit, // Indicates the state machine needs following code units to transit the state.
+        Finished, // Indicates the state machine found a boundary.
+    };
     BackspaceStateMachine() = default;
 
-    // Returns true when the state machine has stopped.
-    bool updateState(UChar codeUnit);
+    // Prepares by feeding preceding text.
+    // This method must not be called after feedFollowingCodeUnit().
+    State feedPrecedingCodeUnit(UChar codeUnit);

[yosin_UTC9, 2016/03/30 04:44:27]

BTW, how do we specify no preceding characters, e.g. we're at start of document?
For previous position usage, it is OK to check start of document at caller and
don't call state machine.
For next position usage, we call state machine at start of document.

[Seigo Nonaka, 2016/03/30 06:58:57]

Yes this is the reason why I can't put NOTREACHED to the feedFollowingCodeUnit.
I introduced notifyEndOfPRecedingText() to be able to notify the end of
preceding text.

 
-    // Finalize the state machine and returns the code unit count to be deleted.
-    // If the state machine hasn't finished, this method finishes the state
-    // machine first.
-    int finalizeAndGetCodeUnitCountToBeDeleted();
+    // Find boundary offset by feeding following text.
+    // This method must be called after feedPrecedingCodeUnit() returns PreparationDone.

[yosin_UTC9, 2016/03/30 01:58:41]

|enum class State| doesn't have member |PreparationDone|.

[Seigo Nonaka, 2016/03/30 06:58:57]

Done.

+    State feedFollowingCodeUnit(UChar codeUnit);
+
+    // Returns the next boundary offset. This method finalizes the state machine if it is not finished.
+    int finalizeAndGetBoundaryOffset();
 
     // Resets the internal state to the initial state.
     void reset();
 
 private:
     int m_codeUnitsToBeDeleted = 0;
 
     // Used for composing supplementary code point with surrogate pairs.
     UChar m_trailSurrogate = 0;
 };
 
 } // namespace blink
 
 #endif