command_buffer: Implement path rendering functions for CHROMIUM_path_rendering

gpu/command_buffer/common/id_allocator.cc

Index: gpu/command_buffer/common/id_allocator.cc
diff --git a/gpu/command_buffer/common/id_allocator.cc b/gpu/command_buffer/common/id_allocator.cc
index 507b14e9af19bfdd298f5b93362dc099f428c5f2..61d2c4a91135381921171a4d1fd0f418fbf77d06 100644
--- a/gpu/command_buffer/common/id_allocator.cc
+++ b/gpu/command_buffer/common/id_allocator.cc
@@ -48,6 +48,71 @@ ResourceId IdAllocator::AllocateIDAtOrAbove(ResourceId desired_id) {
   return id;
 }
 
+ResourceId IdAllocator::AllocateIDRange(uint32_t range) {
+  DCHECK(range > 0);
+  if (range == 1) {
+    return AllocateID();
+  }
+
+  ResourceId first_id = kInvalidResource;
+
+  {
+    // Try to re-use ids from free_ids.
+    ResourceIdSet::const_iterator iter = free_ids_.begin();
+    ResourceIdSet::const_iterator end = free_ids_.end();
+    const ResourceIdSet::size_type size = free_ids_.size();
+    if (iter != end && size >= range) {
+      ResourceId first = *iter;
+      ResourceIdSet::size_type needed_size = range;
+      ResourceId prev = first;
+      ++iter;
+      for (; iter != end && size >= needed_size; ++iter) {
+        if (prev + 1 == *iter) {
+          if (first + range - 1 == *iter) {
+            first_id = first;
+            break;
+          }
+        } else {
+          needed_size += prev - first + 1;
+          first = *iter;
+        }
+        prev = *iter;
+      }
+    }
+  }
+
+  if (first_id == kInvalidResource) {
+    // Allocate after the last id.
+    ResourceId first = LastUsedId() + 1;
+    if (first != 0) {
+      ResourceId last = first + range - 1;
+      if (first < last) {
+        first_id = first;
+      }
+    }
+  }
+
+  if (first_id == kInvalidResource) {
+    // Scan the gaps between used ids.
+    ResourceId prev = 0;
+    for (auto id : used_ids_) {
+      if (id - prev > range) {
+        first_id = prev + 1;
+        break;
+      }
+      prev = id;
+    }
+  }
+
+  if (first_id != kInvalidResource) {
+    for (uint32 ii = 0; ii < range; ++ii) {
+      MarkAsUsed(first_id + ii);
+    }
+  }
+
+  return first_id;
+}
+
 bool IdAllocator::MarkAsUsed(ResourceId id) {
   DCHECK(id);
   free_ids_.erase(id);
@@ -62,6 +127,12 @@ void IdAllocator::FreeID(ResourceId id) {
   }
 }
 
+void IdAllocator::FreeIDRange(ResourceId first_id, uint32 range) {
+  for (uint32 ii = 0; ii < range; ++ii) {
+    FreeID(first_id + ii);
+  }
+}
+
 bool IdAllocator::InUse(ResourceId id) const {
   return id == kInvalidResource || used_ids_.find(id) != used_ids_.end();
 }