diff --git a/js/src/jsopcode.cpp b/js/src/jsopcode.cpp
index 504fc6a14868..ceb86e3b9af1 100644
--- a/js/src/jsopcode.cpp
+++ b/js/src/jsopcode.cpp
@@ -1429,57 +1429,6 @@ js_QuoteString(ExclusiveContext *cx, JSString *str, jschar quote)
 
 /************************************************************************/
 
-StaticBlockObject *
-js::GetBlockChainAtPC(JSScript *script, jsbytecode *pc)
-{
-    JS_ASSERT(script->containsPC(pc));
-
-    if (!script->hasBlockScopes())
-        return nullptr;
-
-    if (pc < script->main())
-        return nullptr;
-    ptrdiff_t offset = pc - script->main();
-
-    BlockScopeArray *blockScopes = script->blockScopes();
-    StaticBlockObject *blockChain = nullptr;
-
-    // Find the innermost block chain using a binary search.
-    size_t bottom = 0;
-    size_t top = blockScopes->length;
-
-    while (bottom < top) {
-        size_t mid = bottom + (top - bottom) / 2;
-        const BlockScopeNote *note = &blockScopes->vector[mid];
-        if (note->start <= offset) {
-            // Block scopes are ordered in the list by their starting offset, and since
-            // blocks form a tree ones earlier in the list may cover the pc even if
-            // later blocks end before the pc. This only happens when the earlier block
-            // is a parent of the later block, so we need to check parents of |mid| in
-            // the searched range for coverage.
-            size_t check = mid;
-            while (check >= bottom) {
-                const BlockScopeNote *checkNote = &blockScopes->vector[check];
-                JS_ASSERT(checkNote->start <= offset);
-                if (offset < checkNote->start + checkNote->length) {
-                    // We found a matching block chain but there may be inner ones
-                    // at a higher block chain index than mid. Continue the binary search.
-                    blockChain = &script->getObject(checkNote->index)->as<StaticBlockObject>();
-                    break;
-                }
-                if (checkNote->parent == UINT32_MAX)
-                    break;
-                check = checkNote->parent;
-            }
-            bottom = mid + 1;
-        } else {
-            top = mid;
-        }
-    }
-
-    return blockChain;
-}
-
 namespace {
 /*
  * The expression decompiler is invoked by error handling code to produce a
@@ -1740,7 +1689,7 @@ JSAtom *
 ExpressionDecompiler::findLetVar(jsbytecode *pc, unsigned depth)
 {
     if (script->hasObjects()) {
-        JSObject *chain = GetBlockChainAtPC(script, pc);
+        JSObject *chain = script->getBlockScope(pc);
         if (!chain)
             return nullptr;
         JS_ASSERT(chain->is<BlockObject>());
diff --git a/js/src/jsopcode.h b/js/src/jsopcode.h
index 3f019c99aeb0..ed75130495f7 100644
--- a/js/src/jsopcode.h
+++ b/js/src/jsopcode.h
@@ -777,11 +777,6 @@ GetNextPc(jsbytecode *pc)
     return pc + GetBytecodeLength(pc);
 }
 
-class StaticBlockObject;
-
-StaticBlockObject *
-GetBlockChainAtPC(JSScript *script, jsbytecode *pc);
-
 } /* namespace js */
 
 #if defined(DEBUG)
diff --git a/js/src/jsscript.cpp b/js/src/jsscript.cpp
index e1004f988947..b94db57d618e 100644
--- a/js/src/jsscript.cpp
+++ b/js/src/jsscript.cpp
@@ -2894,6 +2894,58 @@ LazyScript::finalize(FreeOp *fop)
         fop->free_(table_);
 }
 
+StaticBlockObject *
+JSScript::getBlockScope(jsbytecode *pc)
+{
+    JS_ASSERT(containsPC(pc));
+
+    if (!hasBlockScopes())
+        return nullptr;
+
+    ptrdiff_t offset = pc - main();
+
+    if (offset < 0)
+        return nullptr;
+
+    BlockScopeArray *scopes = blockScopes();
+    StaticBlockObject *blockChain = nullptr;
+
+    // Find the innermost block chain using a binary search.
+    size_t bottom = 0;
+    size_t top = scopes->length;
+
+    while (bottom < top) {
+        size_t mid = bottom + (top - bottom) / 2;
+        const BlockScopeNote *note = &scopes->vector[mid];
+        if (note->start <= offset) {
+            // Block scopes are ordered in the list by their starting offset, and since
+            // blocks form a tree ones earlier in the list may cover the pc even if
+            // later blocks end before the pc. This only happens when the earlier block
+            // is a parent of the later block, so we need to check parents of |mid| in
+            // the searched range for coverage.
+            size_t check = mid;
+            while (check >= bottom) {
+                const BlockScopeNote *checkNote = &scopes->vector[check];
+                JS_ASSERT(checkNote->start <= offset);
+                if (offset < checkNote->start + checkNote->length) {
+                    // We found a matching block chain but there may be inner ones
+                    // at a higher block chain index than mid. Continue the binary search.
+                    blockChain = &getObject(checkNote->index)->as<StaticBlockObject>();
+                    break;
+                }
+                if (checkNote->parent == UINT32_MAX)
+                    break;
+                check = checkNote->parent;
+            }
+            bottom = mid + 1;
+        } else {
+            top = mid;
+        }
+    }
+
+    return blockChain;
+}
+
 void
 JSScript::setArgumentsHasVarBinding()
 {
diff --git a/js/src/jsscript.h b/js/src/jsscript.h
index 544f3798767f..09d88c489bdc 100644
--- a/js/src/jsscript.h
+++ b/js/src/jsscript.h
@@ -43,6 +43,7 @@ class RegExpObject;
 struct SourceCompressionTask;
 class Shape;
 class WatchpointMap;
+class StaticBlockObject;
 
 namespace analyze {
     class ScriptAnalysis;
@@ -1268,6 +1269,8 @@ class JSScript : public js::gc::BarrieredCell<JSScript>
         return arr->vector[index];
     }
 
+    js::StaticBlockObject *getBlockScope(jsbytecode *pc);
+
     /*
      * The isEmpty method tells whether this script has code that computes any
      * result (not return value, result AKA normal completion value) other than
diff --git a/js/src/vm/ScopeObject.cpp b/js/src/vm/ScopeObject.cpp
index 4997f4022e25..8114c0b89a65 100644
--- a/js/src/vm/ScopeObject.cpp
+++ b/js/src/vm/ScopeObject.cpp
@@ -38,7 +38,7 @@ InnermostStaticScope(JSScript *script, jsbytecode *pc)
     JS_ASSERT(script->containsPC(pc));
     JS_ASSERT(JOF_OPTYPE(*pc) == JOF_SCOPECOORD);
 
-    StaticBlockObject *block = GetBlockChainAtPC(script, pc);
+    StaticBlockObject *block = script->getBlockScope(pc);
     if (block)
         return block;
     return script->function();