Add SkRecord::defrag().

Called by SkRecordOptimize(), this moves all the NoOps to the end and
slices them off.

This implementation with std::remove_if() is linear and doesn't malloc.

No diffs: https://gold.skia.org/search2?issue=1461663003&unt=true&query=source_type%3Dgm&master=false

BUG=skia:

Review URL: https://codereview.chromium.org/1461663003

3 files changed, 16 insertions, 0 deletions

diff --git a/src/core/SkRecord.cpp b/src/core/SkRecord.cpp
index 2d2fa58991..2e03e993b8 100644
--- a/src/core/SkRecord.cpp
+++ b/src/core/SkRecord.cpp
@@ -6,6 +6,7 @@
  */
 
 #include "SkRecord.h"
+#include <algorithm>
 
 SkRecord::~SkRecord() {
     Destroyer destroyer;
@@ -30,3 +31,12 @@ size_t SkRecord::bytesUsed() const {
     }
     return bytes;
 }
+
+void SkRecord::defrag() {
+    // Remove all the NoOps, preserving the order of other ops, e.g.
+    //      Save, ClipRect, NoOp, DrawRect, NoOp, NoOp, Restore
+    //  ->  Save, ClipRect, DrawRect, Restore
+    Record* noops = std::remove_if(fRecords.get(), fRecords.get() + fCount,
+                                   [](Record op) { return op.type() == SkRecords::NoOp_Type; });
+    fCount = noops - fRecords.get();
+}
diff --git a/src/core/SkRecord.h b/src/core/SkRecord.h
index ee10b15784..8901d62e91 100644
--- a/src/core/SkRecord.h
+++ b/src/core/SkRecord.h
@@ -111,6 +111,10 @@ public:
     // need to iterate with a visitor to measure those they care for.
     size_t bytesUsed() const;
 
+    // Rearrange and resize this record to eliminate any NoOps.
+    // May change count() and the indices of ops, but preserves their order.
+    void defrag();
+
 private:
     // An SkRecord is structured as an array of pointers into a big chunk of memory where
     // records representing each canvas draw call are stored:
diff --git a/src/core/SkRecordOpts.cpp b/src/core/SkRecordOpts.cpp
index 8faa45ce56..04c72c32cc 100644
--- a/src/core/SkRecordOpts.cpp
+++ b/src/core/SkRecordOpts.cpp
@@ -22,6 +22,8 @@ void SkRecordOptimize(SkRecord* record) {
 
     SkRecordNoopSaveLayerDrawRestores(record);
     SkRecordMergeSvgOpacityAndFilterLayers(record);
+
+    record->defrag();
 }
 
 // Most of the optimizations in this file are pattern-based.  These are all defined as structs with: