Have heap snapshots throw std::system_error instead of return a bool

Summary:
Instead of returning a `bool` which gives no information about the cause of the error,
return `void` and throw when there's some error.

Another alternative is returning `std::error_code`, but that's less flexible than throwing, and
this API already supports throwing.

Changelog: [Internal]

Reviewed By: jbower-fb

Differential Revision: D19170033

fbshipit-source-id: 870cd996a1a53c94524455f31765c1da99f57a1d

ReactCommon/jsi/jsi/decorator.h

@@ -335,12 +335,12 @@ class RuntimeDecorator : public Base, private jsi::Instrumentation {
     plain().instrumentation().collectGarbage();
   }
 
-  bool createSnapshotToFile(const std::string& path) override {
-    return plain().instrumentation().createSnapshotToFile(path);
+  void createSnapshotToFile(const std::string& path) override {
+    plain().instrumentation().createSnapshotToFile(path);
   }
 
-  bool createSnapshotToStream(std::ostream& os) override {
-    return plain().instrumentation().createSnapshotToStream(os);
+  void createSnapshotToStream(std::ostream& os) override {
+    plain().instrumentation().createSnapshotToStream(os);
   }
 
   void writeBridgeTrafficTraceToFile(

ReactCommon/jsi/jsi/instrumentation.h

@@ -55,16 +55,12 @@ class Instrumentation {
   /// Captures the heap to a file
   ///
   /// \param path to save the heap capture
-  ///
-  /// \return true iff the heap capture succeeded
-  virtual bool createSnapshotToFile(const std::string& path) = 0;
+  virtual void createSnapshotToFile(const std::string& path) = 0;
 
   /// Captures the heap to an output stream
   ///
   /// \param os output stream to write to.
-  ///
-  /// \return true iff the heap capture succeeded.
-  virtual bool createSnapshotToStream(std::ostream& os) = 0;
+  virtual void createSnapshotToStream(std::ostream& os) = 0;
 
   /// Write a trace of bridge traffic to the given file name.
   virtual void writeBridgeTrafficTraceToFile(

ReactCommon/jsi/jsi/jsi.cpp

@@ -99,12 +99,14 @@ Instrumentation& Runtime::instrumentation() {
 
     void collectGarbage() override {}
 
-    bool createSnapshotToFile(const std::string&) override {
-      return false;
+    void createSnapshotToFile(const std::string&) override {
+      throw JSINativeException(
+          "Default instrumentation cannot create a heap snapshot");
     }
 
-    bool createSnapshotToStream(std::ostream&) override {
-      return false;
+    void createSnapshotToStream(std::ostream&) override {
+      throw JSINativeException(
+          "Default instrumentation cannot create a heap snapshot");
     }
 
     void writeBridgeTrafficTraceToFile(const std::string&) const override {