current program can be null in ES2/ES3 contexts.

gpu/command_buffer/service/program_manager.cc

Index: gpu/command_buffer/service/program_manager.cc
diff --git a/gpu/command_buffer/service/program_manager.cc b/gpu/command_buffer/service/program_manager.cc
index ca0725533b0a172b70f41b72dd2e2b2dc1f54fc2..632f93aaeb46dc1b39b9243e9ad2ccc92313b54b 100644
--- a/gpu/command_buffer/service/program_manager.cc
+++ b/gpu/command_buffer/service/program_manager.cc
@@ -310,6 +310,11 @@ Program::Program(ProgramManager* manager, GLuint service_id)
       fragment_output_written_mask_(0u) {
   DCHECK(manager_);
   manager_->StartTracking(this);
+  uint32_t packed_size = manager_->max_vertex_attribs() / 16;
+  packed_size += (manager_->max_vertex_attribs() % 16 == 0) ? 0 : 1;

[piman, 2016/07/25 20:04:04]

nit: uint32_t packed_size = (manager_->max_vertex_attribs() + 15) / 16
Avoids an if test, extra modulo, and is standard pattern to round up.

+  vertex_input_base_type_mask_.resize(packed_size);
+  vertex_input_active_mask_.resize(packed_size);
+  ClearVertexInputMasks();
 }
 
 void Program::Reset() {
@@ -327,8 +332,14 @@ void Program::Reset() {
   attrib_location_to_index_map_.clear();
   fragment_output_type_mask_ = 0u;
   fragment_output_written_mask_ = 0u;
-  vertex_input_base_type_mask_.clear();
-  vertex_input_type_written_mask_.clear();
+  ClearVertexInputMasks();
+}
+
+void Program::ClearVertexInputMasks() {
+  for (uint32_t ii = 0; ii < vertex_input_base_type_mask_.size(); ++ii) {
+    vertex_input_base_type_mask_[ii] = 0u;
+    vertex_input_active_mask_[ii] = 0u;
+  }
 }
 
 void Program::UpdateFragmentOutputBaseTypes() {
@@ -370,27 +381,17 @@ void Program::UpdateFragmentOutputBaseTypes() {
 }
 
 void Program::UpdateVertexInputBaseTypes() {
-  max_vertex_attribs_ = manager_->max_vertex_attribs();
-  uint32_t packed_size = max_vertex_attribs_ / 16;
-  packed_size += (max_vertex_attribs_ % 16 == 0) ? 0 : 1;
-  vertex_input_base_type_mask_.resize(packed_size);
-  vertex_input_type_written_mask_.resize(packed_size);

[Zhenyao Mo, 2016/07/23 16:10:40]

We don't need to resize every link because they never change size.  So move it
to Program constructor.  This probably isn't a perf gain at all, but
conceptually I feel this is cleaner.

[yunchao, 2016/07/24 04:52:13]

Acknowledged.

-
-  for (uint32_t ii = 0; ii < packed_size; ++ii) {
-    vertex_input_type_written_mask_[ii] = 0u;
-    vertex_input_base_type_mask_[ii] = 0u;
-  }
-
+  ClearVertexInputMasks();
+  DCHECK_LE(attrib_infos_.size(), manager_->max_vertex_attribs());
   for (size_t ii = 0; ii < attrib_infos_.size(); ++ii) {
-    DCHECK(ii < max_vertex_attribs_);
     const VertexAttrib& input = attrib_infos_[ii];
     if (ProgramManager::HasBuiltInPrefix(input.name)) {
       continue;
     }
     int shift_bits = (input.location % 16) * 2;
-      vertex_input_type_written_mask_[ii / 16] |= 0x3 << shift_bits;
-      vertex_input_base_type_mask_[ii / 16] |=
-          InputOutputTypeToBaseType(true, input.type) << shift_bits;
+    vertex_input_active_mask_[ii / 16] |= 0x3 << shift_bits;
+    vertex_input_base_type_mask_[ii / 16] |=
+        InputOutputTypeToBaseType(true, input.type) << shift_bits;
   }
 }