Initial CL to create Reorder command builder behind a flag

src/gpu/GrReorderCommandBuilder.cpp

Index: src/gpu/GrReorderCommandBuilder.cpp
diff --git a/src/gpu/GrReorderCommandBuilder.cpp b/src/gpu/GrReorderCommandBuilder.cpp
new file mode 100644
index 0000000000000000000000000000000000000000..3ba95d7c966858501e0aed9bd09f4c803b3c2496
--- /dev/null
+++ b/src/gpu/GrReorderCommandBuilder.cpp
@@ -0,0 +1,46 @@
+/*
+ * Copyright 2015 Google Inc.
+ *
+ * Use of this source code is governed by a BSD-style license that can be
+ * found in the LICENSE file.
+ */
+
+#include "GrReorderCommandBuilder.h"
+
+static bool intersect(const SkRect& a, const SkRect& b) {
+    SkASSERT(a.fLeft <= a.fRight && a.fTop <= a.fBottom &&
+             b.fLeft <= b.fRight && b.fTop <= b.fBottom);
+    return a.fLeft < b.fRight && b.fLeft < a.fRight &&
+           a.fTop < b.fBottom && b.fTop < a.fBottom;
+}
+
+GrTargetCommands::Cmd* GrReorderCommandBuilder::recordDrawBatch(State* state, GrBatch* batch) {
+    // Check if there is a Batch Draw we can batch with by linearly searching back until we either
+    // 1) check every draw
+    // 2) intersect with something
+    // 3) find a 'blocker'
+    if (!this->cmdBuffer()->empty()) {
+        GrTargetCommands::CmdBuffer::ReverseIter reverseIter(*this->cmdBuffer());
+
+        do {
+            if (Cmd::kDrawBatch_CmdType == reverseIter->type()) {
+                DrawBatch* previous = static_cast<DrawBatch*>(reverseIter.get());
+
+                if (previous->fState->getPipeline()->isEqual(*state->getPipeline()) &&
+                    previous->fBatch->combineIfPossible(batch)) {
+                    return NULL;
+                }
+
+                if (intersect(previous->fBatch->bounds(), batch->bounds())) {
+                    break;
+                }
+            } else {
+                // TODO temporary until we can navigate the other types of commands
+                break;
+            }
+        } while (reverseIter.previous());
+    }
+
+    return GrNEW_APPEND_TO_RECORDER(*this->cmdBuffer(), DrawBatch, (state, batch,
+                                                                    this->batchTarget()));
+}