Revert of current program can be null in ES2/ES3 contexts.

gpu/command_buffer/service/program_manager.h

Index: gpu/command_buffer/service/program_manager.h
diff --git a/gpu/command_buffer/service/program_manager.h b/gpu/command_buffer/service/program_manager.h
index 36bc94e84d1e7f4ce0f7dcd4f9cc6339aeb2471c..a3fd9f2e6e48534487f7cea6d7ba32f763d6cd0c 100644
--- a/gpu/command_buffer/service/program_manager.h
+++ b/gpu/command_buffer/service/program_manager.h
@@ -397,18 +397,24 @@
   // See member declaration for details.
   // The data are only valid after a successful link.
   uint32_t fragment_output_type_mask() const {
-    return fragment_output_type_mask_;
+      return fragment_output_type_mask_;
   }
   uint32_t fragment_output_written_mask() const {
-    return fragment_output_written_mask_;
+      return fragment_output_written_mask_;
   }
 
   // The data are only valid after a successful link.
-  const std::vector<uint32_t>& vertex_input_base_type_mask() const {
-    return vertex_input_base_type_mask_;
-  }
-  const std::vector<uint32_t>& vertex_input_active_mask() const {
-    return vertex_input_active_mask_;
+  // Return 16 attributes' base types, in which the attribute
+  // specified by argument 'loc' located.
+  uint32_t vertex_input_base_type_mask(GLuint loc) const {
+      DCHECK(loc < max_vertex_attribs_);
+      return vertex_input_base_type_mask_[loc / 16];
+  }
+  // Return 16 attributes' type written masks, in which the
+  // attribute specified by argument 'loc' located.
+  uint32_t vertex_input_type_written_mask(GLuint loc) const {
+      DCHECK(loc < max_vertex_attribs_);
+      return vertex_input_type_written_mask_[loc / 16];
   }
 
   // Update uniform block binding after a successful glUniformBlockBinding().
@@ -498,8 +504,6 @@
 
   const FeatureInfo& feature_info() const;
 
-  void ClearVertexInputMasks();
-
   ProgramManager* manager_;
 
   int use_count_;
@@ -577,13 +581,14 @@
   // by an output variable, 0x00 if not.
   uint32_t fragment_output_written_mask_;
 
+  uint32_t max_vertex_attribs_;
   // Vertex input attrib base types: FLOAT, INT, or UINT.
   // Each base type is encoded into 2 bits, the lowest 2 bits for location 0,
-  // the highest 2 bits for location (max_vertex_attribs - 1).
+  // the highest 2 bits for location (max_vertex_attribs_ - 1).
   std::vector<uint32_t> vertex_input_base_type_mask_;
   // Same layout as above, 2 bits per location, 0x03 if a location is set
   // by vertexAttrib API, 0x00 if not.
-  std::vector<uint32_t> vertex_input_active_mask_;
+  std::vector<uint32_t> vertex_input_type_written_mask_;
 };
 
 // Tracks the Programs.