Rename InstructionsReader to ImageReader for symmetry with ImageWriter.

runtime/vm/snapshot.h

Index: runtime/vm/snapshot.h
diff --git a/runtime/vm/snapshot.h b/runtime/vm/snapshot.h
index 8e387efee7447bb738d5f92419883f1826e21062..edbe4cbc824275a89d3224e01152a73fdf5bef43 100644
--- a/runtime/vm/snapshot.h
+++ b/runtime/vm/snapshot.h
@@ -337,10 +337,9 @@ class BackRefNode : public ValueObject {
 };
 
 
-class InstructionsReader : public ZoneAllocated {
+class ImageReader : public ZoneAllocated {
  public:
-  InstructionsReader(const uint8_t* instructions_buffer,
-                     const uint8_t* data_buffer)
+  ImageReader(const uint8_t* instructions_buffer, const uint8_t* data_buffer)
       : instructions_buffer_(instructions_buffer), data_buffer_(data_buffer) {
     ASSERT(instructions_buffer != NULL);
     ASSERT(data_buffer != NULL);
@@ -355,7 +354,7 @@ class InstructionsReader : public ZoneAllocated {
   const uint8_t* instructions_buffer_;
   const uint8_t* data_buffer_;
 
-  DISALLOW_COPY_AND_ASSIGN(InstructionsReader);
+  DISALLOW_COPY_AND_ASSIGN(ImageReader);
 };